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Messages - Rob Freeman

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1
Reflectors Telescopes Forum / Re: A well cooled mirror is a thing of beauty
« on: February 08, 2018, 03:51:55 AM »
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My stars are always too bloated for me to see worms.
I don't recall seeing thermal issues, but likely that is because I don't do much solar system viewing.
10" SCT always give amazing DSO views compared to Newts. I think that is only because they are automatically at high power, where detail is, whereas with Newts I tend to do low power and hesitate to go higher. I need to learn to use the aperture.


Badly bloated stars are almost always a sign of thermal issues in the telescope. And it's absolutely not only something seen during solar observing. It is an EXTREMELY common problem in newtonians, maksutovs and SCTs, even in some refractors,

Clear skies!
Thomas, Denmark
A lot depends on the size of the newt and your climate. With my 6-8" newts that have sat outside and cooled by natural convection for 60 minutes, i see hot optic/tube current effects so seldom that it takes me a few seconds to recognize what I am seeing when it occurs. 30 minutes is often enough except in winter.

I had forced air cooling on one 8". It shortened the cool down period, but running the fan after the was scope cooled produced no discernible difference.

I have another 8" that's front heavy with many EPs and finders. If I keep it, i might add a fan in the rear to balance the scope, and it will also accelerate initial cooling by a few minutes.

In severe cold, which is rare here, I am not going to stay outside long and use a small refractor for quick looks unless something unusual is going on in the sky.

2
I've been doing this 50+ years and I never stop learning. Though it's slowed down a bit, it hasn't stopped. The curve is uneven, depending.

To try and remember which what and when is just too much work.

3
Mounts Questions & Expirience / Re: Polemaster final alignment help
« on: February 02, 2018, 07:25:38 PM »
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There is something I don't understand.
le manual says:
7.When using the PoleMaster, Should I stopt the mount RA tracing or not?
No. It is best to keep tracing during using the PoleMaster.

​Thefacelessmen says that the mount should be powered down.

What is the best way to use polemaster?
Thank you
Vince

My guess is that it is to keep field rotation out of the equation during the time you are aligning. Of course, I have no idea if that is true.

I've done it both ways and unscientifically felt that my results were better with it on, but I have no real data to support that.

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Mounts Questions & Expirience / Re: Discmount or Desert Sky
« on: February 02, 2018, 06:45:09 PM »
I’ve been using a DSV-3 for 2 years.

The mount has supper smooth motions WITHOUT the slow motion controls. The motions are smoother than the Universal Astronomics mounts that I own. The slow-motion controls can keep an object near the center of the field or make small adjustments at high power without touching the telescope and without using the drift/push/drift method. The tension can be adjusted and the controls always follow the scope and user in azimuth remaining in easy reach. You can also replace the knobs with longer cables for refractors if necessary.

Do I use the slow motion controls all the time – no. But for high power centering, etc. even with the mount’s ultra-smooth motions they do come in handy, especially with my longer FL Mewlon.

My DSV-3 easily holds my Mewlon 210 and Tak 120 (about 20-pounds each) for twin scope viewing. The ability to use 2 scopes is nice when you want to compare images, or evaluate/compare scope performance, and is great for solar viewing using one scope for Ha viewing and another scope for white light viewing. Of course you can use the mount with a single scope as well.

Balance is critical for best performance as it is with most alt/az mounts.

I got my mount in 5 weeks but I hear it is taking 4 to 6 months to get one nowadays.

Bob

5
General Astronomy & Observing / Re: Planetary Conjunctions
« on: January 31, 2018, 11:39:49 AM »
May 7/8 ,around midnight ,Jupiter in the Moon glow , through clouds and a Moon Corona - Coolpix S3300 on Velbon tripod.

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Ziridava

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Beginners Forum / Re: Why do I need a 32mm eyepiece?
« on: January 31, 2018, 04:28:00 AM »
I like eyepieces. I think I'm going to start collecting them ;-D

Even though I have better EP's, the 30mm 2" Zhumell is probably my most used eyepiece, and I'd love to get something even wider, say 34mm 68 degree. Having the ability to see large swaths of the sky is a great thing to be able to do, and the views can also be spectacular (even if a bit smeared at the edges lol).

Everyone has their own opinion about EP's. There is no one "right" EP for everyone.

7
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A hobby is just that; a hobby. When one doesn't have interest, don't force it, or you will learn to think of astronomy as "work", rather than enjoyment. No shame in taking a break; when the interest does return, it will once again be enjoyable.
That's a very good point to remember - we often feel a sense of duty to our hobbies, but they are supposed to be fun, not just more work.
A hobby is just that; a hobby. When one doesn't have interest, don't force it, or you will learn to think of astronomy as "work", rather than enjoyment. No shame in taking a break; when the interest does return, it will once again be enjoyable.

I understand how the OP feels. I live in a dismal white zone for light pollution with trees everywhere, and the nearest star parties happen in... a red zone.. whee... Not their fault - anywhere along the I-95 corridor in the Mid Atlantic is basically horrible for astronomy. The trees and bad weather don't help, either.
Right on Matthew, Take abreakonce a while,, who cares,,, don't be so hard on yourself !! There's nothing wrong with it. I took a break a few years ago and came back into it with renewed enthusiasm and vigor !!

8
ATM, Optics and DIY Forum / Re: Ordered Antares secondary
« on: January 30, 2018, 11:16:56 PM »
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At the risk of not reducing your cognitive dissonance I would just like to point out that you could have spent $100 less for a 1/15 secondary. But what would you have done with that extra $? Not much, other than take your significant other out for dinner and a movie, maybe. How much more you would see with a 1/30 vs 1/15 is the key question and one you will have to resolve for yourself.


It is my understanding that secondary's are specified by surface error rather than wave front error so a 1/30 secondary has a 1/15 wave error and a 1/15th secondary has a 1/7.5 wave error, that's in one orientation.  A 1/7.5 wave error starts to be significant..

Jon

Hi Jon,

I have a 1/30th wave 3.1" Antares secondary in my 18"/F4.5 OMI mirrored Obsession. In my 14"/F4.5 Zambuto mirrored SDM I have a 2.6" ULS Quartz Protostar Secondary and in my 10"/F5.3 Suchting mirrored SDM I have a 1.83" ULS Quartz Protostar Secondary.

The Protostar Secondary's aren't graded like the Antares ones, just certified as being better than 1/10th wave P/V and supplied with an interferometer certificate.

I can guarantee you that regardless of spec, the Protostar Quartz secondaries perform at least as well as the 1/30th wave Antares secondary. In fact the optical pair of Zambuto Primary and Protostar Quartz Secondary in my 14" SDM; are as good as I've ever seen in any Newtonian telescope and I've seen a lot over the past 45 years. That is confirmed by the 30 or so US visitors that attend the Ozsky Star Safari every year. The general comment is "that scope is stunning". Steve Gottlieb couldn't walk away from it at Ozsky 2016, notwithstanding there were plenty of bigger scopes on the field.

The point of the foregoing? I am just not sure what's in all the numbers re Secondary spec.

Cheers,

9
The truss poles would indeed need to be reduced in length and the secondary mirror would have to be over-sized.

There are some benefits from doing this. The height of the eyepiece is reduced, and the back focus of the Kellor allows more than enough room to put a filter wheel in the light path. And as mentioned, the Kellor can be used in more than one scope, so if you want a small, medium, and large scope,

The system can also be returned back to native focal length and used with conventional eyepieces and coma corrector by using an extension tube.

While the secondary has to be made as much as about 35% to 40% (depending on the native speed, about 40% for native f/4, to fully illuminate an APS-C sized chip, but far less for visual use) this should not have a serious effect on most targets. Very small, low contrast targets could suffer some definition loss though.

The point though is that I do believe that there is an increasing trend in the desire for faster mirrors.

About a year ago on this very forum, I had said as much. I had said that the next wave in telescopes will be smaller systems using fast mirrors.

I am a big fan of Mel Bartel's RFT writings, and his logic is impeccable. A properly designed fast scope with a correctly selected Ethos eyepiece can make a fantastic RFT.

Much of the demand though is going to come form EAA use (video camera near real time viewing) and from image intensifer users (real time image and faster is better and very fast is better still because >we don't care about no stinking exit pupil!

Modifications are indeed necessary, but this is cheaper than a custom mirror and custommade OTA.

And not saying it will do everythinganyone would ever want to do, and not saying that there are no compromses, but I am saying that if speed is the goal, sub aperture corrector is a possible solution for some people some of the time.

10
Wow, lot's of good inputs from experience observers. FYI...I have a Celestron 4" f/9.8 refractor that I use as my grab scope. Stars are nice and sharp with good eyepiecs in it. I only find a small amount of CA on just the very brightest stars. Star clusters are great in the scope. Not much of an issue on the moon, just some CA on the edge of the limb. Lot's of fine detail on the creators and mountains. Jupiter is pretty good to and not enough color to keep me from seeing detail. Also, you can buy a $50 filter that will turn down a lot of the purple fringing if you think you need it.

Anyway hope you make a decision soon. there are a lot of good things to observe. Jupiter is very high in the sky and lots of actin on the moons now. Saturn is now rising after 10 pm.

11
Mounts Questions & Expirience / Re: AP Mach1, AP1100 or GM2000
« on: January 29, 2018, 10:14:16 PM »
Mileage will vary with unguided imaging as it is affected by many variables. Local seeing, refraction parameters, ect. Unguided for paramounts, and ap mounts will be limited to your local conditions. Most are only able to get 5-15min. unguided with ap and paramount, from what I'm seeing here on CN. I've had several ap mounts, and I always had to go the guided route, even with short f/l. 5 minutes max. for ap 1600 and an FSQ 106 edx. If you live where there are pristine skies, then mounts other than 10u will go unguided longer. Others may argue this point, but this has been my experience here in the Midwest. 

 10u routinely achieve 30 min.+ unguided images as the mount takes into account temperature and barometric pressure along with a model that provides up to 100 pts. You'll definitely want a blue stick or mbox with the mount. They provide the refraction information that is fed to the scope. By the way, blue astro (per's old website is now or about to be reactivated by baader). There are several modelling programs out there that have been developed by users of the 10u mounts. It's one of the things that I never understood about 10u: Why they didn't develop their own modelling software.

 For longer f/l (> 1000 - 1100mm), the 10u will need guiding in most cases. Some with longer f/l do achieve unguided images at 25 -30 minutes, but I suspect this is under ideal conditions. For guiding I use the IF ONAG and sx ultrastar, SGP, and PHD2.

 The downside to 10u is the forum support and the long /frequent vacations that are annoying with the EU. If you live in the U.S., Tolga is an excellent vendor and will be with you step by step, even at night should that be necessary. He is a vendor for all three of the manufacturers that you are interested in and will provided unbiased and experienced recommendations. Wish I had purchased my mount from him.

 Can't speak to sb mounts, but Astrophysics does provide excellent customer service and are easily available during the work week via phone...........................Gunny

12
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Just thinking about it...I think that the set screw marks on the upper body might be some sort of attachment for a cell phone camera for eyepiece projection photography? Just a shot in a dark.

Yes, and they are called tele-extenders, not to be confused with TelXtenders which is Mead'e's name for their telecentric barlows (like Powermates). I still can't figure out why Meade gave them that name!

13
I really liked the idea of an 18", but whe push came to shove and I mean that literally as well as metaphorically I went for the 15" Ob. Classic because it's the largest size classic you can view with your feet on the ground at the zenith unless you are really tall, lifting the mirror box is just about manageable without ramps and it easily fits it the back of my small hatchback. I also figured it would function on most nights similarly to my 10" scope in terms of seeing. It definitely takes longer to set up than a typical solid tube dob and the thicker mirror takes longer to reach equilibrium, but on nights of better transparency it's worth it. I can tell you, that since I have gotten my 8", the 15" sees less use. If I had a more permanent set up in a dark site like Jon that would be different. Of course, if I had that I might consider more aperture, too.

Chesterguy

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Beginners Forum / Re: Another newbie eyepiece question
« on: January 25, 2018, 03:59:44 PM »
The non duplication is really the most weighty factor, but also the 3X will give you that nice little bump in magnification on those nights that can support it. Apart from that I can't think of any other compelling reason.

Clear skies!

CB

15
Beginners Forum / Re: Hotech Collminator worth the $$$?
« on: January 25, 2018, 01:12:45 PM »
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Wow, that was quite a post! Now I'm going to have to go back and re-check my Hotech laser! In my 10" Dob, I only use the laser in the 2" mode so I don't have to concern myself with errors in the 1.25" adapter. Seems to fit very snugly, but now you say that the two rubber expansive rings may not be 100% parallel? Is that what I'm reading?As far as his comment regarding how well his GSO eyepieces fit in the barlow. I have a couple of eyepieces that do it to. They are Brandon and they fit into a focus tube like a glove! I notice the
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That's quite a family you have there Jon! Looking good for 70.air sucking comment he made. They fit so perfectly that I don't even have to tighten the retaining screw if I don't want to! All my other expensive EP's do not fit as well as the Brandons.

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