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Old 12-07-2015, 10:28 PM
DJT (David)
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GSO RC8 Carbon fibre. .This is how it goes

I bought one of these a couple of years ago and have had quite the journey learning how these work. Nailed it last night fixing focuser tilt.

So this is a simple step by step guide to getting the damn things to work well.

1) buy the following items at the same time as purchasing the scope
A) secondary dew heater and controller
B) Set of Losmandy weights that will sit below the nose of the scope for balance. Don't attach to the scope, attach to your saddle plate if you can..ps, buy an extended saddle..these scopes are arse heavy.

2) Stuff you really should consider
A) moonlight 2.5 focuser or similar, with stepper motor for Focusmax control. I went this way because I chose to go CCD. A DSLR should be fine with the stock focuser.

B) Takahashi Collimator ( the web will give you lots of hints, laser stuff, hall of mirrors etc but the simplest is with the tak colimating scope , use all of the extension rings you get with the GSO and extend the focuser all the way out to see what needs to be done). Get in touch with precise parts for the threaded connections to focuser.

C) Precise parts connector from Moonlight to tak Collimator

3) This is 1628 mm focal length scope. Buy an OAG. I purchased an MMOAG from astrodon, heavy duty but the CCD and FW is a tad heavy. Worth every cent. Moonlight do a series of threaded adapters including one to the telescope side of the MMOAG

4) buy the GSO Tilt ring. It took me 2 years to get to this, gawd knows why..you need it.This really was the final lightbulb moment. This should not be an extra but part of the standard kit.

5) don't bother with a flattener..when you add a flattener you are throwing glass into the imaging train where it's not needed. You will get flare, and other reflective artifacts because no one has come up with a half decent one for a CCD with a large chip with this scope. With an APS chip size a flattener is not required with the RC8. With an STL6303, the curvature is not bad at all. You can get away with a very small crop.

if you treat the extras as an upgrade path to something that gives you performance that really isn't far off from a high end Scope then you are on the right track. You can chose to spend a bit of cash on these but when you do, they sparkle and they are still less than a third of the price of a higher end scope.

Bog standard carbon fibre GSO RC8 ..$ 1300
Secondary dew heater.".........................$. 100
DEW controller."....................... ......$. 150
Tak Collimator......................... .......$. 250
Precise Parts adapter.......................$. 130
Astrodon MMOAG............................$. 980
moonlight adapter to MMOAG......,,....$. 90
GSO Tilt Ring RC8...........................$. 90
Upgrade for AP900 Saddle plate......$. 300
Losmandy Counter weight set...........$. 150
Moonlite Focuser with stepper motor..$. 950

Total Outlay............................. .......$ 4,400

Hopefully still worth it.

Enjoy.

Last edited by DJT; 14-07-2015 at 05:45 AM. Reason: correction on adapter to MMOAG
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  #2  
Old 13-07-2015, 06:21 AM
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lazjen (Chris)
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A good write up, thanks for sharing.

I'm not sure how much of your experience can translate to GSO RC10CF, but I can confirm several of your statements, including:

* switching to a different focuser - I did Moonlite as well

* I've had issues with a flattener exactly as you mention. I think it's also occurred with a reducer as well, but I'd have to verify that to be sure.

* I agree with the weight issue, but I've managed to get by, I think it helped that I added a dew shield to the top that added weight. I've also got a small weight on the scope's top bar that I can slide back and forth for finer weight adjustments. It could also be that the larger RC10 has the balance point in a different spot.

* I haven't got a dew heater yet although I've had some problems with dew in the past. The dew shield however seemed to reduce those a lot.

* As far as I can tell, I haven't had any issue with tilt in the system and I haven't done any collimation yet. Now that I'm getting the observatory setup and a permanent install, I can check and investigate this further.
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Old 13-07-2015, 07:40 AM
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RickS (Rick)
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Hutech have an adapter from the Tak Collimating scope to T-thread. If you search IIS you'll find a couple of threads where I have mentioned it. I don't remember what it costs but it's a lot less than $130. Every little bit helps

Cheers,
Rick.
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Old 13-07-2015, 03:07 PM
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I agree with everything except the flattener statement.

I found when using a QSI583 on an RC8 there was still visible field curvature. That was nearly 6 years ago. I confess to being pedantic to star shapes though. The RC8 responds well to the Tak 2.7" flattener. It corrects the field nearly perfectly.

I am still investigating a flattener for the RC12 as the 3" one from Telescope Services does not work. It is sitting on my scope right now but it does not correct the field on a 11002 sensor. I have to crop the field to get a half decent field. I might as well have bought a 6303E.
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Old 13-07-2015, 08:40 PM
DJT (David)
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Quote:
Originally Posted by Paul Haese View Post
I agree with everything except the flattener statement.

I found when using a QSI583 on an RC8 there was still visible field curvature. That was nearly 6 years ago. I confess to being pedantic to star shapes though. The RC8 responds well to the Tak 2.7" flattener. It corrects the field nearly perfectly.

I am still investigating a flattener for the RC12 as the 3" one from Telescope Services does not work. It is sitting on my scope right now but it does not correct the field on a 11002 sensor. I have to crop the field to get a half decent field. I might as well have bought a 6303E.
Hi Paul
Thanks, I should probably have qualified that statement given I have only experienced using smaller sensors. I got burnt with a flattener. Got the PP adapters, put it on and whilst flat, I got the most horrendous hot spot plus other artifacts. Good to know about the tak though. If I get a bigger chip then its worth knowing. (actually, remembering as you had it in your write up if I recall)

Added a single sub from tonight, 20 mins in Ha uncropped with a quick stretch in PI. Close enough. ps, the 6303e is a sensitive little devil.

Quote:
Originally Posted by RickS View Post
Hutech have an adapter from the Tak Collimating scope to T-thread. If you search IIS you'll find a couple of threads where I have mentioned it. I don't remember what it costs but it's a lot less than $130. Every little bit helps

Cheers,
Rick.
Good to know, Rick. I remember seeing the thread a while back. Not begrudging the investment made so far as am enjoying the images coming through at the moment. Having said that, am all for the cheaper options. I know of at least one good imager who just used a standard cheshire on hers. Unbelievable how quickly it adds up though


Quote:
Originally Posted by lazjen View Post
A good write up, thanks for sharing.

I'm not sure how much of your experience can translate to GSO RC10CF, but I can confirm several of your statements, including:

* switching to a different focuser - I did Moonlite as well

* I've had issues with a flattener exactly as you mention. I think it's also occurred with a reducer as well, but I'd have to verify that to be sure.

* I agree with the weight issue, but I've managed to get by, I think it helped that I added a dew shield to the top that added weight. I've also got a small weight on the scope's top bar that I can slide back and forth for finer weight adjustments. It could also be that the larger RC10 has the balance point in a different spot.

* I haven't got a dew heater yet although I've had some problems with dew in the past. The dew shield however seemed to reduce those a lot.

* As far as I can tell, I haven't had any issue with tilt in the system and I haven't done any collimation yet. Now that I'm getting the observatory setup and a permanent install, I can check and investigate this further.
Cheers. Pretty certain the cause of mine was around the connection between the extension tubes and the focuser.
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Last edited by DJT; 14-07-2015 at 05:48 AM.
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