Author Topic: Visual accessories for Advanced VX EdgeHD 8"  (Read 476 times)

Kash Dickens

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Visual accessories for Advanced VX EdgeHD 8"
« on: December 28, 2017, 02:17:18 AM »
First of all....HELLO!!! I am brand new to the world of astronomy. I barely ordered a Celestron Advanced VX EdgeHD 8" yesterday, and can't wait for it to arrive. Several very long days of research went into this decision with numerous factors. At the end of the day, this scope was the largest my wife would tolerate and I wanted something that would grow with me as I discover what I want.

Okay...so I have a shiny new telescope...now what? First on the list is visual accessories I guess. I started doing research and wow...am I overwhelmed yet again. Please help!!!

• This is my understanding: OTA -> Visual Back -> Diagonal -> Barlow (optional) -> filters (optional) -> eye piece (Am I missing something?)
• Does Edge HD 8 have 2” male threads on back? So the 1.25” visual back provided is pretty much an adapter?
• Is there any reason not to just buy 2” visual back for 2” diagonal for 2” Barlow for 2” eye piece? Forgot cost for a minute. 2" are supposed to be better I thought, but it looks like 1.25" have their purpose as well with higher power?
• Would a 2” 25mm EP yield an object the same size to my eye as a 1.25” 25mm but with more area around it (assuming 2” had a larger FOV of course)? So basically, the viewing area would be bigger resulting in bigger image like a 50” TV vs a 35” TV?
• If I want to truly maximize the overall visual quality with a 2” EPs, do I want everything from the SCT to the EP to also be 2”? Will using a 1.25” visual back, diagonal, then use adapter for a 2” 2x Barlow and finally 2” EP reduce overall visual quality? As I dig into forums on this subject, there are a ton of new words I need to learn, and it seems very complicated.
• A few examples of products I found to help understand all of this:
 o 2” visual back: http://agenaastro.co...sct-thread.html
 o 2” prism star diagonal (what does prism and star mean?): http://agenaastro.co...al-2956100.html
 o 2” 2x Barlow: (includes 1.25” adapter) http://www.telescope...mpression-rings
• People advertise Celestron focal reducer for astrophotography, but what about visual experience? http://www.celestron...s-7x-edgehd-800
This reducer basically gives me a 2nd telescope for about $300 which should have a significant impact on all my visual accessories since overall magnification would be impacted?
• If I were to invest in a few (3-4) quality EPs & a 2x Barlow, what would I get to maximize visual experience on EdgeHD 8? What would be highest and lowest mm EP recommended specifically for this scope? I want to experience everything that this scope can offer me so moon, planets, galaxies, nebula, etc. Maybe 1 or 2 high power 1.25” (unless there are 2” versions but I don’t think I saw any), and a couple low power 2” EPs?
• When people say “deep sky” are they referring to everything beyond our solar system, or looking at a huge expanse of sky (i.e. a ton of stars all in one shot)? I say this because people always stress larger FOV and lower F#s for deep sky.
• I think I read that with high-end optics, filters become obsolete?



Akida Holland

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Re: Visual accessories for Advanced VX EdgeHD 8"
« Reply #1 on: January 01, 2018, 06:49:39 AM »
Hello and congratulations on your new scope. I am also rather new to this hobby, having only bought my Nexstar 6SE (a smaller cousin to your scope) earlier this year.

My first advice is to go slow. It is easy to think you are "missing things" and that it's important to fill in all the perceived gaps before you can enjoy your equipment. Assuming your scope came supplied with a 25mm Plossl eyepiece, I would say you only really need three things:
A dew shield - SCT scopes are notorious for dewing up and cutting your observing session short
A power supply
A shorter focal length eyepiece in the 10-15mm range
Regarding 2" accessories, these are only useful when trying to "open up" the view at focal lengths greater than around 25mm (in your scope, magnifications less than around 80x). Below (above) that number, 1.25" gives you the exact same experience. Your scope is very good for high-power views of planets and smaller deep sky objects (DSOs). You can stick with 1.25" accessories and be very happy for a very long time. SCT scopes are not particularly good for rich field (wide sky) views. Some people try to overcome this using 2" accessories, but results will be limited - you can't fundamentally change the optical design of the scope.

Regarding the reducer/corrector, afaik this won't work with EdgeHD, so you can strike that one off your list ... but it is another way of "opening up" the view and essentially making your scope behave as if it has a shorter focal ratio. Your scope has a focal ratio of f/10, which is considered long or "slow." With a r/c it would have an effective ratio of f/6.3, which is somewhat fast. A really fast scope would be f/4 or even lower. For the same given aperture, a fast scope will show a wider slice of the sky - or a "richer field."

Deep sky objects (ie. things outside the solar system) are many and diverse. Even with your 2000mm f/10 scope, the vast majority of DSOs will fit in the field of view of your scope while using a 1.25" eyepiece. Some of the largest nebulae won't. The Andromeda Galaxy won't (well, actually that kind of depends - the core of it will, and in urban/suburban light pollution the core is all you will see anyhow). Star fields within the Milky Way won't. Only you can decide how important it is to squeeze every last degree/minute of view out of your equipment.

Regarding filters, they have their uses but they are by no means essential. There is some great information here and here.

Enjoy your telescope. Spend a while looking at the kinds of objects it's best at (globular clusters ... oh my!) The 2" accessories will still be there later.

headsbigwardsubs

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Re: Visual accessories for Advanced VX EdgeHD 8"
« Reply #2 on: January 04, 2018, 10:40:20 AM »
Hello DIDI,

Welcome to the world of astronomy! I think you got the basic visual kit about right. I started with 1.25' eye pieces and was impressed. From my research and usage there is a difference between the FOV of the EP depending on the maker say 50 to 100 degrees or so. They come in different sizes (1.25 and 2) inches. The 2 inch diagonal and EP can add significant weight to your set up but it should not be difficult for your mount. Usually the 2 inch variants are also more expensive.A focal reducer should reduce your f-stop to about f7 or f6.3 if i remember right and it also reduces the focal length. It really depends on your interest. Do you want to see more then you go with the full focal length. A barlow helps increase magnifying power of the EP but you reach a point when it becomes useless.

Here is more on that: http://www.telescope...using-eyepieces

About the Deep sky, it is a term referring to very distant objects beyond the solar systems. Nebulae and Star clusters and what not. FOV is what you can see of that object depending on you telescope and EP combination.

Try this for FOV: http://www.12dstring.me.uk/fov.htm

By the way, using a barlow can dim your visual experience and maybe you can focus on better EP to help you see more of what you want to observe. The more light passing through the EP the better experience. Here is where the FOV of the EP comes into play. Of course a 2 inch EP would technically allow more light to pass to your eyes.

ifaclidis

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Re: Visual accessories for Advanced VX EdgeHD 8"
« Reply #3 on: January 04, 2018, 07:55:10 PM »
Geez Didi,

How about some baby steps, so you can learn what factors matter most for your type of observing?
If your scope comes with a 1.25" visual back, diagonal, and EPs, stick with that size for awhile. Going to two inch size will allow you to go to focal lengths and EP designs giving wider true fields of view, but observe with the stock ones and a couple of good eyepiece additions to see if going wider matters to you. Image quality is not a factor between 1.25" and 2" EP sizes, generally speaking. (Note that some examples of excellent eyepieces may only be available in one size.)

Deep Sky Objects are those beyond the Solar System. Extended objects are those presenting a large angular width on the sky. The planets, planetary nebulae, most galaxies, etc. present a relatively small angular size.

This coming Spring, the brighter planets will be nicely placed for viewing in the evenings. Time to gear up for that opportunity now. One filter I might recommend that you get now would be a variable polarizing filter, which can allow you to cut the brightness of the Moon and planets to comfortable viewing levels. A Lumicon UHC filter, or similar can be helpful in pulling out details of planetary nebulae and diffuse nebulae. But, that's mainly what a UHC is used for. Not planets or galaxies or star clusters.  I'd skip the color filters, for now.

Your scope is a 2032mm FL f/10 system. So this means that a 10mm eyepiece would give 203x, which is 25x per inch of aperture. That would be a usable magnification on many clear nights, and give decent views of Jupiter, Saturn, etc.

For an even higher magnification, look for an eyepiece in the 6-7mm range. 6mm would give you 339x or 42x per inch. On nights with good seeing, that can be usable, but might soften the image a bit more than you like.

If I read the Celestron site correctly, your scope only comes with a 40mm eyepiece? Kind of an odd choice by Celestron, as a 40mm 1.25" eyepiece's field of view is truncated by the eyepiece barrel. I'd suggest buying an eyepiece in the 25-30mm range.

If you are eventually going to switch to 2" accessories, you may not want to spend a ton on 1.25" eyepieces, etc. For good images with decent FOV at affordable prices, consider
the Celestron X-Cel LX line. You might pick the X-cel LX 25mm, 9mm, and 7mm for starters, to supplement your 40mm (Plossl?). The Meade 5000 HD60 eyepieces are equivalent.

Skip getting a barlow, for now. Your scope focuses by moving the primary mirror. That means that each time you switch from barlow in to barlow out you'd have to turn the focus a fair bit to refocus. For a scope like yours with a 2 meter long focal length, I don't think that a barlow isn't really necessary, IMO.

Jim

ardrivunla

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Re: Visual accessories for Advanced VX EdgeHD 8"
« Reply #4 on: January 09, 2018, 06:08:05 AM »
I appreciate the comments. An additional question (not sure if I will ask this correctly) is what is the most amount of sky I can see with an 8" EdgeHD. In another post, someone said the max on a 6SE was 1 degree. Is mine a litter more since I have a bigger tube?

I think I understand now where I want to go 1.25" vs 2". As already stated, my viewing needs will dictate that. I just wanted to know if I was going to go for wide FOV 2" lenses, if a 1.25" diagonal was going to reduce the overall quality?

I was digging into eye relief and exit pupil from another post and that along with max viewable sky for my scope will atleast dictate "optimal" sized EPs for both extreme ends of viewing.

As I learn more about FOV...I am seeing that a 40mm 1.25" is odd as well. I think a 25mm and 10mm 1.25" would be good purchases. I do want to get a full view of the Andromeda galaxy though...so 30+mm 2"?

Corey Howell

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Re: Visual accessories for Advanced VX EdgeHD 8"
« Reply #5 on: January 09, 2018, 11:45:43 PM »
Quote
Try this for FOV: http://www.12dstring.me.uk/fov.htm

wow....this is amazing. After just a few minutes on this thing I have a really good idea on what I need. The best part is it helps me understand FOV much better. Looks like I really need a wide FOV EP now for the large DSOs.

On another note, my EP isn't very useful for all the pretty stuff

Christopher Patel

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Re: Visual accessories for Advanced VX EdgeHD 8"
« Reply #6 on: January 10, 2018, 01:40:22 AM »
Quote
In another post, someone said the max on a 6SE was 1 degree. Is mine a litter more since I have a bigger tube?


Other way. The longer the focal length, the smaller the True Field of View. See this page and this post for a bit of background info that will help you understand how any given eyepiece will govern what you see. You might also want to download and install Stellarium as well as the "ocular plugin" to play around with.

Key takeaway: your scope has 2000mm focal length. Even a 2" 30mm eyepiece with 100° Apparent Field of View will only yield 1.5° True Field ... and that's a $1000 eyepiece by the way. Don't get hung up on seeing the whole of Andromeda with your scope. Every other galaxy in the sky will handily fit in the field of a 1.25" eyepiece.

teirazaro

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Re: Visual accessories for Advanced VX EdgeHD 8"
« Reply #7 on: January 10, 2018, 01:47:49 AM »
Quote
Quote

In another post, someone said the max on a 6SE was 1 degree. Is mine a litter more since I have a bigger tube?


Other way. The longer the focal length, the smaller the True Field of View. See this page and this post for a bit of background info that will help you understand how any given eyepiece will govern what you see. You might also want to download and install Stellarium as well as the "ocular plugin" to play around with.

Key takeaway: your scope has 2000mm focal length. Even a 2" 30mm eyepiece with 100° Apparent Field of View will only yield 1.5° True Field ... and that's a $1000 eyepiece by the way. Don't get hung up on seeing the whole of Andromeda with your scope. Every other galaxy in the sky will handily fit in the field of a 1.25" eyepiece.
I don't think I am understanding you correctly, or I asked my question wrong. I am told a scope will have a max degree FOV it can handle so don't bother getting an EP that will take you past that because it won't work. What degree FOV is max for the EdgeHD. That wil help me determine the EP that will render the largest FOV with the max magnification. I hope I am saying this right.

tidutamar

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Re: Visual accessories for Advanced VX EdgeHD 8"
« Reply #8 on: January 10, 2018, 04:13:55 AM »
Congrats on your 8" Edge, I did this 3 years ago and had alot of the same questions.While your waiting for the arrival of your Edge, down load " Stellarium" @ stellariun .org  a great tool for learning and finding objects in the night sky that you have questions about. Early on I purchased a Baader Mark III zoom which helped me zero in on the magnification of the EP's I would like to purchase. I believe that saved me on trial and error. And, as JGass mentioned a variable polarizing filter.       
Kaye

handthedemo

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Re: Visual accessories for Advanced VX EdgeHD 8"
« Reply #9 on: January 10, 2018, 08:35:15 AM »
Quote
I don't think I am understanding you correctly, or I asked my question wrong. I am told a scope will have a max degree FOV it can handle so don't bother getting an EP that will take you past that because it won't work. What degree FOV is max for the EdgeHD. That wil help me determine the EP that will render the largest FOV with the max magnification. I hope I am saying this right.


I guess I have two answers to your question, the technical one and the philosophical one. Let's start with the philosophical one:
No telescope is excellent at all things. There are tradeoffs. The (wonderful) telescope that you bought comes with the tradeoff that it maxes out at ~0.8° TFoV with the stock 1.25" optical train. It seems to me that the very first thing you want to do with this scope is to make it do things it quite frankly wasn't designed to do. This way lies madness. If widefield views are your top priority, you bought the wrong scope. Return it and buy something different.
Now the technical one
Take a good look at the links I provided in my post above. Specifically, download the Eyepiece Buyer's Guide spreadsheet and look for the absolute biggest field stop you can find. Then use the equations found in the other link to determine the maximum true field of the C8
One final clarification. You say you are looking for an "EP that will render the largest FOV with the max magnification." Those are two opposing goals. The largest FOV is attained through the minimum magnification. Conversely, high magnification yields a tiny TFoV.

riaherrvodo

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Re: Visual accessories for Advanced VX EdgeHD 8"
« Reply #10 on: January 10, 2018, 09:46:51 AM »
Quote
Quote

I don't think I am understanding you correctly, or I asked my question wrong. I am told a scope will have a max degree FOV it can handle so don't bother getting an EP that will take you past that because it won't work. What degree FOV is max for the EdgeHD. That wil help me determine the EP that will render the largest FOV with the max magnification. I hope I am saying this right.


I guess I have two answers to your question, the technical one and the philosophical one. Let's start with the philosophical one:
No telescope is excellent at all things. There are tradeoffs. The (wonderful) telescope that you bought comes with the tradeoff that it maxes out at ~0.8° TFoV with the stock 1.25" optical train. It seems to me that the very first thing you want to do with this scope is to make it do things it quite frankly wasn't designed to do. This way lies madness. If widefield views are your top priority, you bought the wrong scope. Return it and buy something different.
Now the technical one
Take a good look at the links I provided in my post above. Specifically, download the Eyepiece Buyer's Guide spreadsheet and look for the absolute biggest field stop you can find. Then use the equations found in the other link to determine the maximum true field of the C8
One final clarification. You say you are looking for an "EP that will render the largest FOV with the max magnification." Those are two opposing goals. The largest FOV is attained through the minimum magnification. Conversely, high magnification yields a tiny TFoV.
I really appreciate your responses. They are very informative.

I do want to be clear that having a large FOV is not my priority. All I was trying to do is to determine the widest FOV that this scope works with so I know what I am getting into when I start looking at EPs. The motive for my initial post and 2" and large FOVs was mainly due to the numerous posts that show that this scope is not meant for that...so just trying to figure out absolute limitations. I would have posted a similar post related to smaller FOV and magnification if I went the route of the 8" NEWT (which is what I was weighing this against).

piatimascomp

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Re: Visual accessories for Advanced VX EdgeHD 8"
« Reply #11 on: January 10, 2018, 10:16:10 AM »
I have all the formulas laid out now and digging into that awesome spreadsheet provided and looking at TFOV now. Let me try and use an EP example to ask my question in a different way. Perhaps you already answered and I just can't process the answer.

Celestron Luminos ultra wide field 31mm states that it provides a true field of 1.25 for my scope. Will my scope actually enjoy a TFOV that high? As I mentioned in another post, someone with a 6SE was told the limitations of their scope would never process a TFOV larger than 1 degree now matter what EP they put in their scope. If I wanted to get the EP that provided the larger TFOV that my scope could ever actually handle, should it be .85, 1, or can it actually process this EP that I mentioned. I don't want to spend $240 on this EP to find out that I can't actually see anything beyond a TFOV of 1 degree even though the math says otherwise. Does this make more sense?

Quas Padilla

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Re: Visual accessories for Advanced VX EdgeHD 8"
« Reply #12 on: January 10, 2018, 11:54:25 AM »
Hi DIDI. I have the EdgeHD 800 with AVX mount. I've had it about two months now and have "upgraded" a couple of elements to fit the way I want to observe. First I changed the diagonal to a High Point Quartz 2" so I have the two inch size available to me for 2" eyepieces. Then I purchased a Baader Hyperion Zoom for multiple lengths without the huge cash outlay.A Hyperion Barlow was added for a bit more pull in. While I've looked at a HD focal reducer that's a bit into the future. There is a T adapter and Nikon T ring waiting to be tried out on a clear night. I knew what I wanted to do then went and purchased the items. If you are doing planetary work your list may be different. If you want to do DSO work you will need to possibly add a couple of filters to your list. The one thing is to be comfortable in your decision. Try not to let a negative view of a product or type of product dissuade you from using it if you feel comfortable doing it. It could very well give you the results you are looking for. Your EdgeHD will give you many hours of pleasurable viewing.

geblusandde

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Re: Visual accessories for Advanced VX EdgeHD 8"
« Reply #13 on: January 10, 2018, 03:22:42 PM »
Thanks for the response. I am digging into the EdgeHD white paper now. I wish I wasn't such a research nut. I can't make a purchase until I know the technology behind it all and this is way more than I ever thought it would be. All my other little hobbies was significantly less work. I think I have started to reach my limits with PC time (so says the wife).

acoplochop

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Re: Visual accessories for Advanced VX EdgeHD 8"
« Reply #14 on: January 10, 2018, 10:12:24 PM »
Since you state that you are brand new to amateur astronomy, I am concerned that you are getting too hung up on numbers, before your first scope has even arrived.

Remember that just because eyepiece A has a wider AFOV than eyepiece B, it does not mean that the views of eyepiece A will be better - or even as good as B, especially at the edges of the field. Also, in some cases, in order to SEE the edges of the FOV of extremely wide eyepieces, you may have to move your head around. In other words, in some cases you won't see the entire view at eye one position.

That said, I can tell you that if your scope just comes with one eyepiece: 40mm, you are immediately going to wish that you had one or two shorter eyepieces. If you only buy one more very soon, I recommend that you pick one in the 9-12mm range.

Have you looked through other folks' amateur telescopes? If not, you need to know that visually, most objects will not show noticeable color. Many deep sky objects will appear as dull or no color "faint fuzzies", with limited detail revealed. The problem is the limitations of the human visual processing system. Your brain processes new images every 1/30th of a second or so, and the portion of your retinas that produce the most details are portions which are not as sensitive to low light conditions as the surrounding part. I wouldn't want you to be surprised by the fact that you don't see all the details and colors that you see in the astrophotos that folks post. [ But do spend time enjoying the details of objects like the Orion Nebula! You'll see detail and some color there. ]

Didi, Look through some of the entries on the CN Sketching Forum. These sketches by experienced observers should give you a fair idea of how objects will look through your telescope. It may help you set your expectations to a proper level.Always remember that YOU are an important part of the amateur telescope set up. If you are not comfortable and relaxed at the telescope, you are unlikely to spend much time at the eyepiece for a given object. Telescopes - and especially GEM-mounted ones - will put the eyepiece at awkward locations at times. An adjustable height chair, and warm clothing are valuable parts of an amateur astronomer's gear.

JimP.S. You do have a red flashlight, I hope.