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Topics - postbypopect

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Mainly posting this for curiosity and getting your thoughts. As I am asked for feedback on beginner GOTO scopes all the time i'd like to understand these two scopes below a little more. For the beginner quite a few people recommend a non goto dob or an alt az refractor, but given my better familiarity about cassegrain telescopes I am usually itching to recommend a cassegrain of some type and I think that is totally fine . Sure they have the disadvantage of them having a constrained slow f/ratio and you do have dew issues to figure out with the corrector being on the front, but overall i'm smitten with my Evolution C8, so when people at outreach events or new astronomers joining our area club ask me for a recommendation for something well under $1000, i'm usually itching to tell them to find a used C8, but lately i've wondered about 5" cassegrains (both MCT and SCT) for ease of portability as well as what one can truly see. The aperture is more than most decent refractors that can be had under $1000. They are great on planets which in many cases is what people like to see first and then dabble in more deep sky. And they come in packages with usable GOTO mounts with similar electronics as I have so I can help them through some of the initial newbie headaches to get them started.

One of my friends has a Levenhuk 105 Mak on a similar mount to the Orion Starseeker which is similar to the 127 SLT and it tracks very nicely. He uses it for EAA and some nice planetary stacked imaging. For the cost and size of that little scope i've been really very impressed. He even runs it on batteries quite frequently and gets decent run time.

I've seen a lot of recommendations for the 5SE which instead of a Mak-Cass it is a 5" Schmidt Cass, but what about the less expensive 127 SLT? Any love for the 127 SLT?

The aperture is the same for the two scopes below, but the focal length of the Mak 127 SLT is longer (1500 vs 1250 on the 5SE SCT) and the f/ratio is slower on the 127 SLT (f/12 on the 127 SLT vs f/10 on the 5SE). I've also heard that while you need to still collimate a Mak they are even less susceptible to losing collimation than comparable size SCT's. For the record my 8" SCT Evo purchased in Feb 2016 is still holding its factory collimation even after multiple tumble bumble trips in the car to the dark site, so this argument between holding collimation on Maks and Schmidts may be moot

To frame this a little better I'm interested mainly about the difference in real dark site or backyard experience between these two scopes-I really could care less about technical jargon or arc seconds of accuracy..we are talking 5" beginner scopes here-what's the real experience difference? I'm thinking of both beginners or as a grab and go for someone with a larger scope that would like something they could keep setup or "minimally" stored. For similar sky conditions and targets list including higher Mag objects like the Moon, Saturn, Jupiter, Lagoon and Orion Nebula, M13 and M3 and M11 what would the difference in what one actually sees? Is the 5SE really worth $250-270 more than the 127 SLT???

Both mounts use spur gear drives not worm gears, so i'm not sure that would make a difference. Both are alt/az Nexstar Electronics. Maybe the 5SE has a better tripod and stiffer mount, but on something like this would that really change the experience? Assume that both are setup on grass not concrete.

Head to Head Shootout!!!
Nexstar 127 SLT (Some suppliers have this as low as $439!)

Nexstar 5SE (Usually sold for $699)

Jon Thomas

I was googling polar alignment when I ran across this:Technique for Telescope Polar AlignmentUS 20120307356 A1AbstractA polar scope for a telescope mount includes a reticle having a pattern with multiple markings that allows users to accurately position pole stars for precise polar alignment. A system and mount may be provided including a polar scope of this kind. The polar scope may be provided with a controller that calculates the apparent position of a pole star, while accounting for errors, such as proper motion, precession of the earth's axis, and/or atmospheric refraction. the drawings it's clear that this patent application covers the polar scope in iOptron mounts. It is also interesting that the described method includes correcting for refraction. I have iOptron mounts and appreciate their polar alignment scopes, but I'm a bit surprised that they are unique.

Beginners Forum / Why do I care about Algol?
« on: December 30, 2017, 04:55:00 AM »
So my astronomical calendar keeps telling me when Algol is at a minimum. I understand about variable stars, but why do I need to care if it's at minimum or maximum? Is there something else that happens accordingly, or is the star just brighter and dimmer?

The scope’s tube end rings are sturdy die cast aluminum, to protect the tube during transport and provide exceptionally rigid support for the optics. The mirror cell’s six-screw push/pull locking collimation system keeps the primary mirror aligned far longer than conventional mirror cells – so you spend more time observing, and less time adjusting the optics. The lightweight optical tube rotates in its felt-lined die cast cradle rings to bring the focuser and finder to the most comfortable viewing position. The mounting rings even include a built-in piggyback mount for wide field astrophotography. The 27” long aluminum optical tube weighs only 10 lbs., making it easy to transport and assemble in the field.


I am asking because the above link is the only place I was able to find this description.

Can someone who owns either the 6" or 8" version of this setup comment on those two points specifically? How strongly do those 6 screws prevent the scope from getting out of colimation. Is it true that you can rotate the OTA easily?

What are your overall "review" comments about this setup?

Hi all,
I recently picked this up for my Nexstar 6se as an upgrade to the one it came with and so far im pretty disappointed. After winning the polar scope alignment war, my next issue that i'm having is the accuracy of the mount is wayyyy off. At this point I can't tell if it me, or an issue with the mount. When doing a two star alignment its about 8 degrees off of target. Which in turn affects the polar alignment process as well.

My method is:
Align the mount to Polaris using the polar alignment scope in the mount, lock down everything.
Bootup, enter the time and date info
Select Two-Star Alignment.
The HC displays Vega. I hit enter and it slews over to Vega and by the time it stops, its about 8 degrees off. I center it in the finderscope, hit enter. Center it in the eyepiece, hit Align.
Next star is Altair. The same thing happens and I use the same steps.
I then add 4 calibration starts.

At this point I should be able to goto anything in the sky and at least have it near center in the eyepiece, only that's not the case. If for example I want to look at Vega, it slews over to it and its way off and nowhere near being close to the finderscope. If at that point I try and polar align the mount, that's also a lost cause. As I understand it, if you're goto alignment sucks, then there's not really a point with trying to polar align.

The stock mount it came with was nearly spot on when doing the goto alignment following the exact steps. The only difference is that it had me manually slew to the star and center and align it. The VX slews automatically to the star and offers the calibration star options. Thats the only difference
This is the current info displayed on the HC in regards to firmware

Reflectors Telescopes Forum / How big a Dobsonian to get
« on: December 28, 2017, 11:39:09 PM »
Hi Guys.I am about to begin construction of my new Backyard Observatory.I am thinking about getting a big Dob for that.Here are the parameters to consider:1. It is going to be permanently standing in the Observatory;2. I will not take it to a Dark Site location;3. I live in the suburbs and suffer from Light pollution (not severe but..);4. I am Disabled. I can walk and stand up but can't climb a ladder and need tosit down every once in a while or occasionally be assisted by crutches;5. I already own the following Telescopes:10 inch f/3.9 Newtonian on an EQ mount8 inch SCT (EdgeHD) on an Evolution ALT-AZ mount5 inch Maksutov CassegrainDo you think I should go for a 20 inch'er or a 16 inch'er?What would be best for me?Thanks,Vat.

Mounts Questions & Expirience / Did Tycho Brahe invent the drift method?
« on: December 28, 2017, 07:30:26 PM »
I am just wondering... Tycho had to polar-align his giant equatorial armillary somehow. It may have been the first instrument in all of history that needed a precise polar alignment, as precise as possible. Surely the drift method would have occurred to him as the obvious way to adjust it. Does anybody know whether that's actually what he did?

If I become curious enough, I'll read hisAstronomiae Instauratae Mechanica and see if he says. Online access to rare books is a Good Thing.

The question is in the title. Are curved spider vanes better and if so then why are they not standard equipment? I do not own (or have ever owned) a reflector and have never looked through one with a curved spider. I am a beginner who would like to know why.

This astromart ad is what peeked by curiosity. http://www.astromart...ified_id=924330

There seems to be an entire industry devoted to supplying upgrades for telescopes. I have no way of knowing if an upgrade is a meaningful improvement or a waste of money. And if an improvement, then how much so? Negligible, modest, substantial, extreme? Then the issue of trying to quantify someones else "substantial" improvement. My eyes and value system might see little to nothing of value while they saw enormous. Does not mean people are always lying or being dishonest, just that we are different.

It gets really complicated.

I'm currently using my Celestron Nexstar 5i on a wedge for AP. The mount is nowhere near great for AP, even with guiding. I have been able to get some good results with the C5 on Orion though.

I will be upgrading to my first GEM mount soon and am leaning heavily towards the iOptron CEM25 (maybe the new CEM25P version). I will be using my C5 OTA (about 7 pounds w/o DSLR) at first. Soon after getting the mount I'll be ordering an AstroTech AT72ED for wider shots and late this year, an AT80 APO for my primary imaging scope.

Since these scopes will be relatively light, I'm fairly confident the CEM25 will do just fine, but I'm nervous about all the issues people have had with it. People seem to love it or hate it. I would consider the Celestron AVX, but I really don't like that it doesn't have proper bearings in the dec axis. I've also looked at the Orion Sirius and sirius pro. While I don't have any major gripes about them, the fact that I can get a new CEM25 with a 2" tripod for $900 is a huge plus for me. I don't make much money so it takes a long time to save up for equipment.

If I were to consider another mount, I'd want a Sirius Pro. But it's $400 more. That would mean several more months of saving and would put off getting the AT72 even longer. My plan is to use this mount for a few years and then get an Atlas Pro and move up to a C8 OTA.

I guess I'm asking for reassurance that the CEM25 will be a decent AP mount for small scopes. If the Sirius Pro would be considerably better, I may suck it up and save up for that. I'm just really excited to get a GEM mount so I can do more imaging with a better mount than what I have now.

Mounts Questions & Expirience / Looking for your Input on a Mount
« on: December 27, 2017, 10:36:12 AM »
So far my research has lead me the Orion Atlas EQ-G Computerized GoTo Telescope Mount on which I intend to mount an Astro-Tech AT115EDT f/7 ED Triplet Refractor OTA along with an auto guider, guide scope and DSLR. I am leaning toward this mainly for use in Astro Photography and it seems to have all of the specifications that would lead me to believe it would be a good stable Platform. I would like any input pro or con. I have not spent a dime yet so I am still in the investigation stage.

This posting got me to wondering why I can easily Binoview with Delos, but not Delites - curious enough to investigate.


I measured these for the comparison: Delite 18.2's, Delos 12's, Delos 17.3's

Some facts:
<ul class="bbc">I can easily see the field stop when Binoviewing Delos.
To see the Delite field stop when Binoviewing, I have to remove the rubber eye cup (even so, not comfortably).
Eye cup diameter is the same for all examples I measured. They use the same caps and rubber.
I used TeleVue's eye relief specs: 20mm across the board.
Now for the math:

Remember your basic Trig: Tan (angle) = opposite / adjacent
Angle a = half of the AFOV
Adjacent = Eye Relief
Opposite = Eye Lens Radius

Let's plug in the numbers
Something's amiss. I wonder if TeleVue is downplaying the Delos eye relief? Regardless, this explains the different comfort levels when I Binoview these.

Light Pollution Topics / Dark as pitch! no light pollution!
« on: December 26, 2017, 10:52:46 PM »
I browse this article from time to time and I thought I'd share a nice encounter.

I live in a suburban city with a population of approximately 700k just outside of Toronto that is 2 million + there are also other suburbs around me with 100s of thousands of people.   White zone light pollution.   About twice a year I had been going to a "dark" site that's in the orange zone.   Seeing the milkyway faintly was amazing.   It was always overwhelming considering I could read the newspaper from my observatory when the roof is rolled off, and watch most of what I could throughout the day.

Well I just experienced the grey zone.   A freshwater Island Named St. Joesph's.   The people is 2k at the winter 4k at the summertime.   My parents bought a home there!   When there was any job I could do that I'd move.   They really do not plan on living there full time but will devote a good deal of time there.   I'll be seeing a lot and the home is on 3 acres and future observatory is not going to be a problem!   The closest city is 75k and approximately 100km away so there are no domes or anything.   Given that it is way up north future growth is very unlikely in my life. 

M42 naked eye appeared then it does in my finderscope here!   It was phenomenal.   Just a couple short hours of clear skies I dip as much as I could.   I'm only an imager and did get a few images.   I do have dreams of a large dob up there one day.

After preparing the imaging rig I moved inside.   The first time I went back out I couldn't believe it.   I couldn't see my range!   It was 100 feet from the home but even with all the inside house lights on I couldn't see that far out.   The largest source of light pollution was the red light on the autoguider.   When that wasn't facing me I couldn't see anything!!!

Ultimately it did cloud and even that was impressive.   Here clouds are orange.   There they're invisible.   It was just like the celebrities simply stopped shinning.   I couldn't tell where the trees ended and the sky began.

There are only a couple neighbors most of that are far away in the distance.   None leave stupid 24/7 lighting on like people here.   I only saw a total of 3 road lights on the entire island.   There is one small gas station and general store.   The closest one was 22minutes from the home in the car.   So miles and miles away...

I'll be back next weekend and plan on going every new moon.   Sure sometimes it will be cloudy but hopefully there will be lots of clear skies.   It's also dead quiet there.   I've started a blog on my own experience there.   It is just so different from here the distinction is well, night and day.

ATM, Optics and DIY Forum / Eyepiece for star testing?
« on: December 26, 2017, 08:09:29 PM »
Hello I was wondering whether any of you have an eyepiece that you especially use for celebrity testing optics?  I'm constructing a 14", f4.9 mirror and celebrity testing it correctly with an 8mm eyepiece is quite the challenge.  I believe I want a 3-5mm eyepiece to acquire the necessary magnification and it would need to be at least a good eyepiece at those high powers (probably not chinese Plossl or Ortho).  I would be willing to shell out a few $$ for this, especially if it might also be used as a working planetary eyepiece after the actuality.  Do any of you have any good suggestions for this?


Beginners Forum / Considering 2 (used) reflectors for 1st scope
« on: December 26, 2017, 09:22:27 AM »
Hello all, I'm considering two utilized scopes for my very first, both are for sale locally for the same asking price ($200).  I'd prefer to stay within this price range as I am uncertain how much time I'll be spending  and I don't want to drop $600 on a scope that ends up being used half a dozen nights per year.  Portability is important, I'd like to have the ability to put it in my car and take it when I go camping but I believe either one is good for this.  My principal interest is watching deep sky objects but I'll obviously spend time seeing the planets and moon.

Both I'm considering are:

Sky-Watcher 6" dobsonian


Orion Skyview 6EQ


Beginners Forum / Proletariat Recommendations
« on: December 24, 2017, 08:16:41 AM »

I'm a long time lurker but decided to make an account here.  I am looking for some guidance.  I have found similar threads but most of the recommendations are over my budget.

About 15 year ago I had been, for a teen, pretty intensely in this hobby.  I had a meade refractor that while not the finest, (could never find out the shaky eq bracket) gave me a great deal of enjoyment and kept me out of trouble.  I bought a barlow and a few eyepieces together with my part time job also has been pumped to see individual craters on the moon, Jupiter's moons, and Saturn's rings.  The orion nebula has been my favorite.

Eventually I found girls and my hobby and gear was left behind.  Now more than ten years later I can feel that the heavens calling.  I have been spending time outside with my eyes and affordable binoculars but I want more.

I have been trolling local craigslist for some inexpensive gear but the pickings are slim.  Overpriced Bushnell/Vivitar/Celestion 60mm for not  less than brand new.

I am looking at these

Orion SpaceProbe 3 http://www.telescope...roductId=102295

Orion GoScope 80mm http://www.telescope...rion goscope 80

Orion SkyScanner 100mm http://www.telescope...roductId=102007

AWB 'OneSky' http://store.astrono...5&amp;products_id=4

Any other recommendations are welcome.  I am looking for something which includes a bracket.  I can build a stand to get a mini dob style mount if I have to.  No kids, I will be the sole user, maybe my wife occasionally but I do not expect her to be overly concerned.  We're a 1 income house so the "One Sky" is the max I can manage.

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