10" RC recommendations?

[Octane]

k, go.

H

[Somnium]

are there many options at 10" (apart from GSO and the million rebrands) ?

[Octane]

That's what I'm trying to find out. :)

H

[gregbradley]

Tak BRC 250 is gorgeous, heavy and expensive although not too bad occasionally 2nd hand.

Carbon Fibre GSO is the obvious one.

Not many start at 10 inches. A 2nd hand 10 inch RCOS.

Orion Optics do a 10 inch ODK I think.

http://www.orionoptics.co.uk/ODK/odkoptimiseddall.html

I suppose RC versus CDK type scopes is worth a look. RC are harder to collimate. ODK are easier. Spot sizes are supposed to be smaller with ODK optics. Orion Optics also offer 1/10th wave mirrors for a relatively small extra cost. ODK optics are faster than RC F6.8 versus F8 or F9.

Mike S Orion Optics UK AG scope seems to have a very good mirror and is a great performer.

F6.8 is fast but not that fussy. As you go shorter F ratios the optics become more fussy very often unless you stick to APOs.

Greg.

[Octane]

I would like to aim for 2m focal length, as I'd like to start shooting galaxies.

Deep Sky Instruments look good, too.

I also understand that the cheaper options would require a $1K investment in a focuser, too.

H

[glend]

Re the GSO, I have the RC08 and it does need to be tuned as out of the box they have issues. You probably will need to buy the collimation ring which the tubes don't come with but apparently the truss version does. Yes the focuser is sus. Whatver RC you buy you'll need a TAK Collimation Scope and adaptor , allow $300-400 for that as well. If GSO be prepared to fiddle with it but they are good when sorted out

[Octane]

Glen, my problem is that I don't know the first thing about collimation. I know that whatever route I go, I'm going to have to learn it. :(

Cheers for the collimation rings/scopes heads up.

H

[lazjen]

I better learn how to collimate one day too as I've never done it. :)

Anyway, if you get a GSO RC10, you will need to get another focuser, so that does add to the cost. Still, I'm quite satisfied with the CF version I've got.

[marc4darkskies]

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

[Camelopardalis]

Unless you're going premium H, get yourself a 5 or 6" refractor :P

[lazjen]

That looks great and has a number of features "built-in" that you need to sort out with the GSO, e.g. the focuser.

I wonder what the price difference is between this and a kitted up GSO version? And if there's much difference in the results achievable?

[glend]

Seriously these top of the line RCs are great instruments but the investment required for someone dipping their toe into RCs is significant. Sort of like learning to drive in a Ferrari. I'd suggest starting with the basic tube version of the GSO and go from there. You will learn alot about RCs through tuning the GSO for your purposes, and not need to be too precious with it. Sure you may need to replace the focuser, and buy a collimation ring, and a few other things but the combined cost is going to be less than a third of what the entry level high end RCs would cost.
I'd like to hear what Paul Haese has to say about this topic.

[DJT]

Interested on the 10 inch options as well for the same reasons as you, H.DSI looked good with their RC till I noted its preorder builds only but I liked the idea of the focuser being on the secondary.

With the GSO, absolutely agree with Glen. Go into it with a plan and the budget to upgrade the focuser, get the collimation ring, the tak scope and the OAG (did we not mention the OAG before? helps a lot for longer focal lengths) and thread everything which will also add to the price.


Must admit though I'm not sure about the 10 compared to the 8 in terms of how the focuser is attached and whether or not that's still an issue. Wheres Paul?

Now what I really want to know is where on earth all of the GSO stock focusers end up? Mines pristine, never used!

[rustigsmed]

Barlow a newt, put a good focused on and still save some cash? :question:

[gregbradley]

2 metres at 250mm aperture is F8 which will be slowish. You'll need to do really long exposures and extra total integration time.

ODK 10 at F6.8 is 1700mm which is pretty close and probably great for most seeing with the current smaller pixelled cameras.

Tak BRC250 worked well with Microline 8300 for galaxies at F5. You can get Tak extenders to lengthen the focal length as well.

Better to use a shorter focal length and smaller pixels.
Shiraz is doing pretty well with galaxies using an F4 250mm Newt.

Deep Sky 2nd hand if you can find one. They bought out RCOS and have discontinued their amateur product line to chase Military jobs.

Bottom line Humi I think bang for buck the GSO RCs whilst perhaps a project are hard to beat. No wonder Deep Sky Instruments changed direction as the GSO product must have killed their sales.

Greg.

[glend]

Maybe we could send them back for a credit? If GSO is serious about these scopes it should either sell them as 'fit for purpose' with a Feathertouch and. Collimation Ring, or offer a stripped version with no focuser but with the Ring. They need to have a think about how these scopes sit in the market and why people want changes.

[Octane]

I've been ogling the ODK10.

By the time you add all the accessories (plates, tube rings, adapters, dew shield), and a focuser, it tops out really, really quickly.

I have a choice between a Paramount or a new telescope. I've longed to do long focal length imaging since I got my first LX90 LNT 8". My G-11 gives me perfect round stars even at 30-minute exposures with MaxIm DL showing quite a flat guide graph, so, there's no problem there.

I'm really torn at the moment. I'm really put off by the whole DIY aspect of the GSO scopes -- all the more because I am a complete gumby when it comes to hands-on stuff. I've always owned quality equipment which has just worked without tinkering. The most I've ever had to do was install a RoboFocus on my FSQ-106N.

I want to be able to bang on my STL-11000M and just start imaging.

The Orion Optics telescopes need 3-4 months lead time as they're built to order, I believe.

Maybe it is time to get my hands dirty and buy a GSO?

H

[marc4darkskies]

You answered your question before you asked it! :lol: The only tinkering you should have to do is collimation. Unless of course you actually ENJOY tinkering.

ODK10 looks okay - shame about the exchange rate though. If you want to capture galaxies, be careful going below 2000mm. I did some at 1760 with my TOA (that's F11.7) with good results but I was never really happy with the image scale (using an STL).

[SimmoW]

H, try contacting Nick Jones on our FB group, he's having a few issues with his GSO RC I think. And yes, I wouldn't worry about upgrading the mount, your results look bloody good with the G11

[AlexN]

Deepsky instruments bought out RCOS and as a result no longer make the rc10c.. Deepsky instruments only make the ruggedised military special rc's. 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. A new focuser, secondary heater, focuser collimation ring dew shield, tak collimation scope etc. Look at some of the images from gso rc's on this forum. Paul's 12" is pulling exceptional images from the sky purely because he invested the money to fix what needed fixing and the time to tweak the setup to be the best it could be.

[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]

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]

Ditto :thumbsup:

[Peter Ward]

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. :screwy:

I suppose you could always hang a counterweight off the secondary :D

[DJT]

Done that, works quite well :P

Email sent requesting further details from DSI

[Octane]

David,

Please let me know if you hear back!

H

[DJT]

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]

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]

Thank you, Greg.

OK, I think I'm set.

I'll just need to get final ministerial approval. :P

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.uk/teaching/phy217/telescopes/phy217_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]

Thanks! Reading.

Any recommendations for shrouds?

H

[Octane]

Hahaha!

I'm already emaciated!

H

[LewisM]

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

[Octane]

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

H

[Paul Haese]

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]

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.

[gregbradley]

Yeah carbon fibre fixes that constant refocus need. I find my CDK17 and the RCOS 12 I had hold focus extremely well once the mirror is close to ambient.''

This is an interesting thread as it highlights the decision making process a lot would be going through for this type of scope. It inevitably winds up with GSO because of the value and the high quality optics. That's probably exactly why DSI switched markets.

Greg.

[Paul Haese]

If you like Charles I can come out one afternoon soon and check the collimation with my tak scope Charles. What type of focusor do you have? Is it a 2" or a 3" and does it have a 2" adapter?




I refocus via automation every 90 minutes or so but the change is barely worth mentioning and more to do with seeing conditions and altitude I think. I found the RC12 quite stable too since I put the mirrors in a truss. In the steel tube is moved around like a wobbly custard.

[Peter Ward]

I guarantee it's flexing....but probably not much at all.

The original design by Serrurier was based on the telescope weighting tonnes, hence no material on the planet was not going to sag...and Serrurier solution was indeed elegant. The instrument load was trivial in comparison.

Barnes Wallis employed a similar principle when he designed the 64meter Parked radio dish. Keeping a rigid hyperbolic shape on a dish that large, is nigh impossible...unless you work with gravity...which he did and employed a twin spiral structure that in bending under load, kept a hyperbolic shape but changed the focal point! Clever stuff!! (the receiver cage is easily moved in/out)

With amateur equipment loads, it's a moot point...well...up to a point. Instrument loads on amateur telescopes however are often not trivial when compared to the weight of the telescope...as is evident by having to toss the GSO focuser.

I'd suspect with modestly heavy cameras (STX16803+FW7+AOX or a similar FLI16803 system) it would be detectable.

My point being...it works, but it's not optimum.

[Paul Haese]

I am not saying that there is no sag. The concept of that type of truss is to cancel out flex and sagging in multiple directions. It should not matter how big the system is, gravity will act in a corresponding way. Besides I am simply reporting I don't see any evidence of sag in my images and that is what really matters.

[Peter Ward]

Yes...but the Serrurier only works correctly if you know what the long and short arm masses are.

Given amateur cameras can weigh from a few grams, to a few kilograms...it's
not possible to design a "one truss fits all"

[Paul Haese]

So is that why you bought a truss in the Alluna Optics scope? :P Some of the spiel you used looks very much like that on your site and on the Alluna Optics site. They claim that sag is eliminated and that many lesser brand names would have sag in them. Sounds a little bit like marketing hype to me. Is your scope designed specifically for your payload? Or are they simply designed to take any payload commercially available. The difference might be very miniscule.

I suppose if you are looking at absolute necessity for precision, then the bells and whistles stuff is great. Though no point in having such a fine scope stuff in a light polluted environment in my opinion. Might as well use a lesser scope.

Budget related like I said at the start.

[Peter Ward]

Err....I don't see the point you are trying to make..... the instrument end of the Alluna's is not a truss. :shrug:

The load bearing (up to 50kg instrument loads) is taken up in quite a different way to ensure optical alignment is preserved.

The secondary supports are a truss system that have little commonality with Serrurier's design.

[cfranks]

Thanks for the offer, Paul. your expertise would be very much appreciated. The RC10C focuses by moving the Secondary mirror so there is just a solid connection at the back-end. I have a Tak. collimation scope but, I hesitate to say, I think it is out of collimation! :shrug: It would be good to compare with another. I will make a new set of adapters when it stops raining up here. My machinery uses 3-phase power and my generator is outside and rain + 415v is not particularly good. I'll get back to you soon.
Thanks again.
Charles

[Bassnut]

Well, if your going to get stroppy ;), how often do you focus Paul, more than once a week?.

[Paul Haese]

You know it is a lot more Fred. Usually between three and four times a night. Budget related optics but still sharp though. :P

[KenGee]

Well worth getting Paul to have a look. I bought their first one and it is a great instrument.

[DJT]

Hi H

Response as follows. Not unexpected but worth a punt.

We've been considering this opportunity and have decided that it does not
warrant our time and effort at this time. I wish we could help but we are
extremely busy and need to be selective of which projects we invest in. I
hope you understand our position. Good luck with your scope.

[Octane]

Damn. :(

GSO it is.

Thanks for following up, mate.

H

[DJT]

cheer up..Paul H just posted a belter with his GSO.

[gregbradley]

+1.

Greg.

[Logieberra]

Hi H. I love my GSO 12" CF truss RC. Some fiddling is required, but I enjoy that part :) I got it strictly to use as a galaxy scope and it really delivers. To my untrained eyes, I'm well pleased with the results from GSO optics.

[glend]

H don't make it sound like your being forced to settle for something second rate, as properly tuned they turn out wonderful images. Since I have sorted out the 'issues' that I had with the collimation on my RC08 I am impressed with what it is now producing with my DSLR. I am so impressed I am now considering upgrading to a RC10 - but the CF tube version to keep the cost within my reach. Just do it.:thumbsup:

[RobF]

Might be worth PM'ing RickS too H about 10" RCs. He was using one in the past and I seem to recall found the focal length challenging in terms of time to gather sufficient light/data. Basically was tough to get sufficient data on a single galaxy in 2 nights.

May not be an issue for you as I understand you run on auto in the backyard over many nights from reasonable skies.

[RickS]

I was using the RC10 with a KAF-8300 and the combination was slowish. It's also a little oversampled for the seeing that most of us get (0.56 arcsec/pixel.) That system would collect signal at about half the rate of my most recent combo of Ceravolo 300 @ f/9 with a KAF-16803.

It was usable but a sensor with larger pixels would be a better match. I think H has a STL11K? That would be a decent match for a RC10 wrt imaging speed although I would expect it to need a flattener and the vignetting would be significant.

Cheers,
Rick.

[KenGee]

I use my RC10 with the sbig11000 with the built in flattener and its a great match.