The thread many have waited for. GSO RC 12

[Paul Haese]

Yes it has been a long time coming. Currently the scope and mount are doing a pointing run. Collimation was near perfect from the last time the OTA was on the mount and I have therefore decided not to adjust it.

The idea of this thread is to examine all things with the GSO RC 12. I will give you my impressions of the entire scope over the coming months. I am going to complete an image this month or next month with this telescope. And; then I intend to do several more images with it should the performance be all that I have hoped for.

So for initial impressions.

The ali tube does shift a lot as it cools. Half way through my pointing run tonight I had to stop and refocus. The scope and mount were still mapping but there were donuts forming in the stars. This was after about 45 minutes from initial focus. Fans are working well though and that would be contributing to the focus shift.

As far as I can tell there are no rough edges or surfaces or any real defect in the finish of the mirrors. Nor is there any problem in the baffle as in the first generation of GSO RC's.

The mounting mechanism (rings and dove tails) appears to be working well and that makes for a cost that can be avoided. It clamps really tightly and allows you to use other instruments above the main scope. On mine I am use the top dove tail to support my mount hub pro.

The focusor I replaced with a Feather Touch unit. In my initial tests with the GSO focusor in place I found just slight movements from one side of the meridian to the other. While for the most part this would be ok to image with my main concern is with the mirrors and I am more than happy to pay an extra 1k for a beefy large 3" focusor. Besides places like AstroTech ship this scope without the GSO focusor.

With collimation I did find that the allen screws in the secondary holder are very stiff and difficult to move. This did make for a bit of stuffing around with collimation, but in reality not as much a problem as it could have been. The screws seem to hold collimation well despite being off an on the mount several times in the last 12 months.

The secondary holder and vanes are very solid and almost bullet proof, but I think this might lead to rather thick diffraction spikes. Time will tell though.

So with that I will post up some images as they come to hand and this thread will form the basis of my long awaited review of this telescope. Stay tuned as wish me clear skies.:)

[Paul Haese]

Well found an issue I have no answer for at present and I am welcome to any suggestions.

The problem is dew on the secondary. On the RC 8 I could put on a dew shield but this scope is too big for that. Is there are dew heater I could use?? Anyone know how i would attach it and where would I put it?

[allan gould]

I had exactly the same experiences with my 10" GSO RC down to the collimation screw tightness. I'm lucky as I found that the metal dew shield off my Meade 10" SCT is a perfect fit for the GSO.
Really looking forward to your image.
Allan

[Joshua Bunn]

How about trying a Kendrick Premier Heater of a suitable diameter, wrap it around the secondary and you could replace the wire with some thinner stuff and strap it to the spider veins?
Any dew on the Primary?

Josh

[bert]

http://www.kendrickastro.com/astro/RCoptics.html

They also have a heater for the primary.

Brett

[naskies]

Thanks Paul - I enjoy reading your thoughts and reviews. From your limited experience with the RC12 so far, would you say it's "just an RC8 with a larger aperture" or are there any fundamental differences?



I had my RC8 pointed near zenith in -4 deg C weather a few weeks ago (no dew shield, no heaters on the mirrors, but one 6" dew strap on the OTA). The primary completely iced over :)



Looks very useful - thanks for the link.

[Marke]

So far I havent had any issues with dew on the 10" , I find as long as I keep the fans going its all good but I do have an orion flex shield to use if needed. I hope they bring out the 12 in CF as I would jump on it . I dont know why they havent it seems odd that the 10 does and the 16 will be CF as well ?

Mark

[jjjnettie]

Don't laugh, but I intend to work out a way to secure one of these to the back of the secondary of my RC.
One single warmer lasts for 10hrs.


http://www.amazon.com/HeatMax-Hot-Hands-Handwarmer-Pairs/dp/B0007ZF4OA


I'm thinking some form of slip cover to put it in, the slip cover has a velcro dot sewn onto it, and a matching velcro dot glued onto the secondary, where it won't get in the way.
It won't look very elegant, but if it works, I don't care.

[g__day]

Paul,

When you say "On the RC 8 I could put on a dew shield but this scope is too big for that" - why is that? Are you saying you can't source a big enough dew shield - or no matter what you use it would be ineffective?

If its the former - you can make your own custom dew shield with thin rubber (like a yoga mat). I did this with 5mm thick mat black foam from Clark Rubber. I cut and joined it using a hot glue gun and on the the join I glued an extra 6 inch wide strip the entire length of the join, for strength. In this way I made a oversized 80cm long dew shield for my C9.25 that has worked prefectly for years.

[Paul Haese]

Thanks guys for the comments I will try to answer the questions.

Josh no dew on the primary. Too much mass for that.

Brett that is just what I am looking for, I will be perfect I have a mount hub pro to control the heat.

Naskies, yes it is very much the same but some issues have been sorted. The 12 does not have baffling to the tube though.

Mark I would consider getting the tube myself.

G-day putting a dew shield on it is a bit impractical. My goal is to have it work remotely and putting a dew shield on it which is likely to be had made will present issues with closing the roof even in the side ways point home position. So yes the dew shield is obtainable, but my thoughts were practicality.

First image.

This image is a stack of 5 images with attrocious guiding. The maxim graph was beset with triangles over the entire depth of the graph. At times the guiding was plus or minus 4 pixels. :eyepop:I tried a lot of guide parameters but would like any advice using the STL11 internal chip guider and what settings are best given my focal length of 2400mm.

That said pointing was pretty good but I need to do some collimating and am considering getting a Tak collimating scope.

The image looks way better at this scale rather than larger.

[Satchmo]

Needs to remember that applying any heat to an optic will bend it and most probably affect the figure- but who knows might improve it :)

[Paul Haese]

Mark RCOS and CDK's come with secondary heaters. I don't think this will be a problem. However, I will keep this in mind.

[riklaunim]

Nice scope and first light.

I've seen it listed in some local astro shops. It has 150 mm (50%) of central obstruction. It would be nice if there was an option with small secondary for small sensors (DS... and planetary :)). Custom made planetary Dall Kirkhams are sill around twice as expensive as this mass made RC.

[Satchmo]

Its a good thing they use zero expansion secondary mirror glass.

[SkyViking]

Hi Paul, I have a 120mm fan blowing air over my secondary instead of a heater. This also eliminates the need for cables going to the secondary holder. It works perfectly every time.
The only time it wasn't enough was with near 100% humidity when a fog bank rolled in shortly afterwards and terminated the session anyway.

[JohnH]

You run the fans during imaging? Does this not cause issues with vibration?

[Marke]

No absolutly none at all , they are pretty small and there is too much mass in the scope for it to be a problem .

++