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Pimping your 102mm gt OTA.. Like what?

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#176 t.r.

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Posted 12 September 2013 - 07:50 AM

It is kind of funny, to load this $60 scope up, with my Leica zoom ($500), dielectric diagonal ($100) and or a binoviewer ($1000)! Everything I stick into the focuser is many times more expensive than the scope itself...but oh, do the accessories ever let the lens loose to perform to its full potential! :grin: The jury is still out, but I may use this scope as my first choice grab-n-go scope over the C6!

#177 spongebob@55

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Posted 12 September 2013 - 07:52 AM

Does someone know what the thread is on the end of the focuser tube? I was thinking of getting a Baader Click Lock if there's one available for those synta threads. Would make it so much easier and precise to rotate the diagonal instead of loosening/tightening 2 screws all the time....
Thanks
Sbob


I am not positive, but I do not think Baader clicklock is made with that thread. because of these recent threads about the C-102 scopestuff is backordered on These


Thanks for that link. I was a bit surprised by how expensive that is, especially relative to the $59. I already put in vinyl bolts but you really have to crank down on them, especially with a quality 2" diagonal and a glass gernade EP. :p I guess this accessory would hold better, especially with the brass bolts, but I think I'll hold off for now. But thanks for the link!
Sbob

#178 Ed Holland

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Posted 12 September 2013 - 10:59 AM

Well my experiment was just that.. an experiment because I had no other flocking material. It worked well enough that I'm happy to leave it in place.

of course I understand the concerns about grit particles, but it seems fairly robust to me.

#179 REC

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Posted 12 September 2013 - 12:38 PM

For the extra weight, I have a 2.5lb ankle weights that I just "wrap" around the front of the tube. I then can slide it up and down the tube the counter balance whatever I'm hanging off the back. Like last night I had a binoviewer and two EP's so it got pretty heavy back there.

#180 REC

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Posted 12 September 2013 - 12:45 PM

Wow, you where up over 180x and still looked good? I'm happy with my ES6.7 for 150x in mine.

#181 REC

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Posted 12 September 2013 - 02:35 PM

How do you like the ES rings on it. Are they pretty light?

Is this the best way to mount it? The 4" dovetail bar is way too short and also not in the right spot on the tube.

Did you have to remove the old dovetail bar to use the ES ring or can you just leave it on?

The GSO focuser sound like a great idea for using my heavy BV on the back of the scope.

Thanks,

bob

#182 buddyjesus

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Posted 12 September 2013 - 03:34 PM

I routinely take mine to 200x on the moon and planets.

#183 Ed Holland

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Posted 12 September 2013 - 04:27 PM

I routinely take mine to 200x on the moon and planets.


Despite the risks, I'm sure :roflmao:

#184 cavefrog

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Posted 12 September 2013 - 05:36 PM

Does someone know what the thread is on the end of the focuser tube? I was thinking of getting a Baader Click Lock if there's one available for those synta threads. Would make it so much easier and precise to rotate the diagonal instead of loosening/tightening 2 screws all the time....
Thanks
Sbob


I am not positive, but I do not think Baader clicklock is made with that thread. because of these recent threads about the C-102 scopestuff is backordered on These


Thanks for that link. I was a bit surprised by how expensive that is, especially relative to the $59. I already put in vinyl bolts but you really have to crank down on them, especially with a quality 2" diagonal and a glass gernade EP. :p I guess this accessory would hold better, especially with the brass bolts, but I think I'll hold off for now. But thanks for the link!
Sbob


I had ordered one and got an email telling me they were backordered for a couple weeks. then a couple days later a GSO 96.6mm dual focus showed up in the classifieds for a good price. I have one of these on a C6R. I found out it fits both scopes.

Theo

#185 Ain Soph Aur

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Posted 12 September 2013 - 06:01 PM

Bah, got an email from Hands On Optics saying the Stellarvue black finders will not arrive until next week. This has been going on since last week, then got an oops response then a new shipment will arrive Friday, then Monday or Tuesday and now next Monday or Tuesday. When I ordered the black Stellarvue finder it was in stock but they shipped a white one. Even the enclosed receipt with the shipment indicated the black model. Oh well... Maybe next week.

#186 BullTerrier

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Posted 14 September 2013 - 07:38 PM

Well.. from the sound of all the posts, looks like you all got good samples of the C102. As for me, mine exhibits an annoying amount of CA. Purple haze around bright stars and green/yellow fringes around the edges of the moon. For me, this instrument will be best used on star clusters and the dso's within it's grasp.
What was I expecting for $59 ? But from what I've been reading, sounds like you folks lucked out with better optics.

Martin

#187 CollinofAlabama

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Posted 14 September 2013 - 11:10 PM

Martin,

Your conclusion à la Gershwin "ain't necessarily so". Different people have different reactions to CA. E.g., I own the Orion Premium Refractor, an F/7 102mm with the "poorer" glass (whichever the worst of the two is, FPL 51 or 53). It's extremely well color corrected compared to an achromat -- believe I read from a Jon Isaacs' post that it's equivalent to an F/21 102mm. In any event, around Jupiter, the moon, and Venus, there is, in fact, a very faint purple glow. Still, it's very, very unobtrusive, as one would expect from an F/20+ 4" achromat. But, there are plenty of APO purists who can't even stomach that. Just not up to triplet (or Newtonian) standards, and that's that. You may simply be one of those intolerant of very much CA. Look, there are folks happy with an Orion 120ST, an instrument I consider good for DSOs, but unacceptable for double star/planet/lunar viewing -- all things that, along with DSOs, I like viewing and don't like being limited from targets by the instrument. A 4" F/9.8 has a WHOLE lot more CA than my 102mm with the poorer, but still ED and not just crown flint glass. Plenty of folks don't mind this level of CA, plenty do. Your own preference just could be a particular intolerance of it, which is neither good nor bad, just you. I'm not saying your particular C102 GT isn't optically defective compared to others, it may be, but it is also just as possible, IMO, that your personal vision doesn't cotton to the misaligned color focus that is CA. Nothing at all to feel bad about. You simply may have higher standards for color purity than others here and that's alright.

To be honest, I'm a little worried about this myself. I've first lighted my C102GT, and it performed quite well, but it was only with double stars and DSOs, which it did up to my 102mm F/7's standards. How will it handle Jupiter this Winter, or even crescent Venus later this Fall, or gibbous Luna this week? Will I still like this scope or be looking at less colorful alternatives? Quite worried about that now, and your post gives me pause, since my standards of color purity are, at F/20+ equivalency, clearly quite high. I'm sure it won't do that well, but will I find the Venus, and particularly Jovian view acceptable? Time will tell.

#188 buddyjesus

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Posted 15 September 2013 - 01:55 AM

I used to think mine had terribad CA due to poor focus but have since collimated the scope and the views are much improved. Imagine my delight when I went from a maximum magnification of 143x on planets to 200x without breaking a sweat!

#189 audioaficionado

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Posted 15 September 2013 - 07:30 AM

If mine has excessive CA, I can't see it. My 60 year old eye lenses must have built in CA filtering (aka; yellowing due to age) LOL. Seriously I doubt there is going to be much difference between production scopes as it's a simple and relatively inexpensive design and not much would go wrong in production. It's possible, but not likely.

#190 REC

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Posted 15 September 2013 - 08:16 AM

I was out last night with mine along with my Dob and SCT and a clear night. Bounced around all three scopes and had great views the the 102g on the moon...sharp and I did not notice much CA except around the edge of the moon against the black of the night. Besides, I was mainly viewing the craters and they looked great. Then later I was cruising the Cygnus to Lyra area and the stars where very pinpoint and pleasing views in my 20mm SWA EP.

Also, it rides very nicely on top of the VersaGo2 tripod I have it on...very smooth movement.

Also, have I told you how great the view is with the 102 on the moon in my BV!

#191 PeterR280

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Posted 15 September 2013 - 09:24 AM

How did you collimate the C102GT? Lens cell is fixed.

#192 audioaficionado

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Posted 15 September 2013 - 11:56 AM

Here's me with mine waiting for Venus and Saturn at the Brothers Oregon star party September 2013.

Posted Image

I had some very nice views with it. Others who had premium scopes said the views through it also looked good to them.

#193 amicus sidera

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Posted 15 September 2013 - 12:07 PM

Nice setup, Steve! Hope you had a great time there.

Fred

#194 buddyjesus

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Posted 15 September 2013 - 01:55 PM

I collimated mine by taking the screws out that connect the focuser to the tube and the screws that connect the cell to the tube. My collimation with them on was off center by an inch! The tube is square for the most part at the cell end so I press the cell firmly and squarely onto the tube so all the collimation is at the focuser end. The focuser end of the tube is off square by about 1/8th inch. I never bothered to redrill holes for the screws as they stay in the tube well on their own. I obviously wouldn't ship the scope this way though if I ever had to.

#195 Noisykids

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Posted 15 September 2013 - 06:12 PM

i took the focuser apart to get that grease out of it. mine did not look like the one shown the tutorial linked in this thread or the other thread. that grease is awful. i tried 91% isopropyl alcohol, denatured alcohol, acetone, plain old dish washing soap, and finally came up from the cellar with a jug of Krud Kutter, which i left on the counter. when we got back from a benefit for a family who lost a son to an as yet uncaught driver, where we won tickets to an ahl hockey game and a gift certificate to a restaurant in the same city, the Krud Kutter was gone. i asked my daughter what she did with it, and she said it was on the porch because it made the kitchen smell like moonshine. that was all the paper towels in the trash brimming with all the other solvents. the krud stuff got most of it off, but i had to chase the rack with the cut off stems of q-tips to get it all out. then i put a little light honing oil on it, which was the only thing i had right there, reassembled it, and it was much smoother. i thought i was going have to reach out to the people at fukushima to send me a couple of tablespoons of "hot" water to dissolve the stuff. can you imagine working with it? your fingers must be permanently sticky in spite of the inevitable gloves.

#196 SkyGibbon

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Posted 15 September 2013 - 07:57 PM

Got mine about a month ago. Flocked inside the dew shield, swapped out the focuser with a GSO rotatable. Got new 100mm rings. I finally got to use it the other night after a month of clouds (monsoon). Seems to be a really nice scope. Pic of that night.

Posted Image

#197 spongebob@55

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Posted 15 September 2013 - 08:24 PM

Got mine about a month ago. Flocked inside the dew shield, swapped out the focuser with a GSO rotatable. Got new 100mm rings. I finally got to use it the other night after a month of clouds (monsoon). Seems to be a really nice scope. Pic of that night.

Posted Image


Very nice and glad you have a good result.
Have you and can you describe how it compares with your ES AR127? I would love to get a 127 or even a 150mm achromat depending.....CA and girth. Can you comment?
Thanks
Bob

#198 PeterR280

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Posted 15 September 2013 - 08:36 PM

I am not seeing CA in the moon picture.

#199 desertlens

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Posted 16 September 2013 - 12:04 AM

The only evidence I've seen of CA on the moon was at the limb and that was minimal. It disappeared when I repositioned my eye a bit. I had a chance for a quick look at Venus through some nasty air and CA was obvious as expected with an object this bright.

#200 SkyGibbon

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Posted 16 September 2013 - 12:49 AM

Very nice and glad you have a good result.
Have you and can you describe how it compares with your ES AR127? I would love to get a 127 or even a 150mm achromat depending.....CA and girth. Can you comment?
Thanks
Bob


Sure. Both do have CA, but I find that it only bothers me if I go looking for it. I don't consider it being a problem on either. I do have a fringe killer and a semi-apo filter, but I don't feel the need to use them most the time. As far as girth, the 127 is quite a bit more wieldy, but it is very managable. With my rings, finder and diagonal in the 127, it comes in about 18lbs. The ES is of course a better quality build and the view is a bit nicer, but it was $580.00 more.

Here is a pic with the 127 the night after.

Posted Image








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