10" RC recommendations?

[AlexN]

Oh, and I know it's the 2nd time I've said it in the past few days but the celestron edge hd sct with an f/7 reducer is a good option too. Lot of people are quick to discount set's these days in the world of budget rc's but honestly look at what Fred achieved with a humble meade 12" acf scope on g11... Those scopes are not to be discounted when looking for a large aperture imaging solution. The only other factor is obviously that you likely want to use your stl11k which may stretch the 11" or 9.25" edge hd field.

[Camelopardalis (Dunk)]

Originally Posted by AlexN

....The only other factor is obviously that you likely want to use your stl11k which may stretch the 11" or 9.25" edge hd field.

Shouldn't be too awful, if we assume the specs are correct, as they both have ~42mm imaging circle. IIRC from the white paper, the 9.25 is better corrected out at the edges but is the only one without a reducer available so far.

[Peter Ward]

Originally Posted by marc4darkskies

http://www.deepskyinstruments.com/truerc/rc10c.html

Ditto

[Peter Ward]

Originally Posted by AlexN

The gso rc's seem great to me and given that you are willing to spend a little extra on upgrading a few things that should be standard......

I find it interesting they decided to made their 16's with a Serrurier truss.

A great concept, but sadly applied with no understanding.

Serrurier truss's assume the loads are constant on the secondary and primary, and are designed to sag equally along the long secondary arm, and short primary arm, thus keeping the optics parallel.

So...let's mention the elephant in the room... or in this case, a heavy camera off the primary mirror end (as you do with big RC's....)

We can now guarantee the optics will no longer be parallel.

I suppose you could always hang a counterweight off the secondary

[DJT (David)]

Originally Posted by Peter Ward

I suppose you could always hang a counterweight off the secondary

Done that, works quite well

Email sent requesting further details from DSI

[Octane (Humayun)]

David,

Please let me know if you hear back!

H

[DJT (David)]

Will do.

Cheers

[Paul Haese]

Just found this thread, busy day and waiting for cloud to clear all night at the obs, so I was a little preoccupied.

My opinion: All this is purely budget related. If you have the budget spend up big and get the bells and whistles. If not GSO is the go.

Me and a few other guys across the planet have practically got all the bugs out of GSO gear for you guys to start buying scopes.

A 10 scope does not come with the camera centring ring on the rear plate, so you need buy the centring ring. It screws on the back of the scope.

You definitely need a focusor. A good one that allows plenty of back focus and stability is what you want. I went top of the range with the Atlas but there are other options available.

Buy a shroud and a secondary dew heater. Both those come in handy.

Easy stuff so far and you will be saving yourself heaps.

Every scope with folded optics needs collimation at some point. Marcus spent a bit of time sorting his out. Travel is going to move them a little and so you need to undertaken the task. Once collimated these scopes hold well. I have checked mine once in the last year and well you see the results I get H. That said, you need to become a collimation king to get the most out of an RC. It's not that hard but takes a little practice. A Tak scope will allow you to collimate in about 10 minutes. If you learn how to use the Tak scope really well, you don't need to do a star collimation (this takes a bit of skill)

If that all seems easy then you're up for this sort of tinkering. Personally I hate tinkering, I just want to image, so I understand your point of view H. GSO scopes are good scopes and if you buy from Bintel, they stand by the product. Feel free to ask me any further questions.

Budget with a good focusor is going to set you back about $8000 with an Atlas focusor, adapters, shroud and dew heater. Still cheaper than the other brands out there. You can make it cheaper still by using a feather touch or moonlite focusor. That will cost around $5500.

[Octane (Humayun)]

Thanks for the advice, everyone!

And, thanks, Paul. I'm glad you chimed in here as I know you're getting great results from your 12".

I think I'm set to buy one.

My next question: truss or tube? What advantage does the truss have over the tube, apart from thermal currents? Does Peter's comment about the heavy camera on the end of the scope warrant consideration? I'll have the STL the STL-FW8 and likely an AO-L and MMOAG (in the future). I think I'll go the Feathertouch for now. The dollar is horrendous for overseas purchases at the moment.

Thanks!

H

[gregbradley]

Truss, I think, is always the way to go. Stronger, lighter, less thermal currents, able to get better air flow and easily closed up with a shroud.
If the truss design was a real problem then Paul's images would not be so sharp. They are so unless he got a good one it does not seem to be a real problem. Surprisingly there does not seem to be a lot of difference between scope builders in the quality of the trusses. I have seen a GSO 12 inch in the flesh and I was surprised at the quality of the truss. It seemed very good and every bit as good as my CDK17 (except for the blue coloured bits!).

https://en.wikipedia.org/wiki/Serrurier_truss

RC's with tubes are a pain. I had a closed tube 12inch RCOS for several years. It sat in the car on numerous occasions at my dark site as it was very easily affected by wind. A truss would have been less affected.

Also the truss gives you something to grab when you adjust the scope on its dovetail for balance and for overall handling installing and removing.
A large tube is very awkward to handle.

Last and of course most importantly, trusses look better! They look more professional.

Greg.

[Octane (Humayun)]

Thank you, Greg.

OK, I think I'm set.

I'll just need to get final ministerial approval.

Thank you, all, so much. You're all wonderful.

H

[gregbradley]

Here's an article describing the Serrurier truss system and the advantages/disadvantages:

http://www.vikdhillon.staff.shef.ac....tel_truss.html

Greg.

[LewisM]

H, you should have asked Yuri, Roland or Markus to make you a 250 APO...

Then Mel would hang you as an art exhibit in the national gallery, suspended only by your.....nevermind

[Octane (Humayun)]

Thanks! Reading.

Any recommendations for shrouds?

H

[Octane (Humayun)]

Hahaha!

I'm already emaciated!

H

Originally Posted by LewisM

H, you should have asked Yuri, Roland or Markus to make you a 250 APO...

Then Mel would hang you as an art exhibit in the national gallery, suspended only by your.....nevermind

[LewisM]

Originally Posted by Octane

Hahaha!

I'm already emasculated!

H

Fixed it for you. You have joined the rest of us in marital parsimony...

[Octane (Humayun)]

Haha. Too early in the morning and typing without thinking. Cheers.

H

[Paul Haese]

Originally Posted by Octane

Thanks for the advice, everyone!

And, thanks, Paul. I'm glad you chimed in here as I know you're getting great results from your 12".

I think I'm set to buy one.

My next question: truss or tube? What advantage does the truss have over the tube, apart from thermal currents? Does Peter's comment about the heavy camera on the end of the scope warrant consideration? I'll have the STL the STL-FW8 and likely an AO-L and MMOAG (in the future). I think I'll go the Feathertouch for now. The dollar is horrendous for overseas purchases at the moment.

Thanks!

H

Truss is definitely the way to go.

From what I have heard the new modified support structure was not needed on the rear plate. This had something to do with the dynamics of the incident of flexure in the mirror assembly. You should be ok with the STL and heavier focusor on board. I think trying to fit in a rotator might be pushing things though. Have a chat with Michael from Bintel and see what he thinks too.

I am using an Astrozap shroud. Works really well.

[cfranks (Charles)]

Hi H,

I have had a DSI RC10C for about 5 years and have really only had one successful image (my fault, not the 'scope). A 4 frame mosaic of Omega Cen. http://www.astrobin.com/full/80259/0/ I haven't used it for 3 years or so since I set it up imaging on a forecasted clear night and went inside for a cuppa. Came out again and it was raining and the primary was like a half-full soup bowl! When I eventually removed the primary mirror, cleaned and very accurately replaced it, I had managed to put it out of collimation. Having no experience there I struggled along until Paul published his work in that area and now I might have finally fixed it. Haven't had a suitable night for > 3 months to test it but here's hoping. One of my favourites, NGC 300, is now rising and it fills my QSI638 perfectly with the RC10C.
Probably my only change, if I had my 'druthers, is to get a CF tube rather than what it currently has. The RC10C seems to require an awful lot of focusing and I would think a CF tube would reduce that.

Cheers

[Paul Haese]

Further to your question re the truss employed. I have found no issues with this design at all. The 12" is using a Serrurier truss and it exhibits no flexure as described by Peter. I am not saying it is not a relevant concern; just that I have not seen anything in my long subs to demonstrate there would be a problem.