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Just an update: I have been out with the RASA on two nights so far – 11th and 13th – and not yet had trouble with dew forming on the corrector plate – even in the absence of a shield. Hiwever, neither was a wet night (it was -1C and -5C respectively) but there were hard frosts (really hard last night). Will update again when I have used it on a night when water is running off the mount or pier.
A friend has tried a Canon 450 on it but nothing bigger yet. The Starlight 56 has too big a body – the issue being the shutter. The Starlight 25 would be a nice start or better still a 35. However, I don’t have access to anything bigger and so cannot oblige. Anyone want to lend me one? 🙂
I think Celestron have said that wings of the focal plane should run off to 60-70% of peak. The 14″ version is better controlled and is corrected better for wavelengths beyond 800nm.
Finally got some quality time with the Celestron 11″ RASA. The attached image is M81 and M82 – though I rather suspect you all knew that. I used a venerable Starlight H18 for 15 unguided 60s frames last night. The focus was a little off – my fault not the scope – and also the camera body is not properly aligned with the focal plane after some changes made to ensure it worked with a Canon lens adaptor. So, this pretty much suggests that someone doing the job properly will get quite a nice result.
I liked the focuser, the quality of the images and the speed of the system, but it has made it very clear I need to sort out the cable mess I have before I go much further. I’m not used to wires coming of the scope front – not after using a RC for a while.
I tried deleting one of the images but lost both, so two it is…
Sounds very nice. Have wondered about corrugated as an alternative to the stuff used for conservatory roofs. Ensures good airflow of course.
I think the USAF observatory on Haleakala has it sorted. The roof opens and the circular walls are lowered to expose the whole sky. Don’t think I could make that work in our garden though. 🙂
If anyone is likely to be interested, but nothing will happen for a few months as we moved house in December and I have the new one to sort out (plasterer due tomorrow, new boiler next month, kitchen to rebuild etc) – theres always stuff needs doing. Thats the real world. 🙂
I have promised to post a first impression on the Celestron 11″ RASA I sometimes use. Tonight would have been perfect, but my poorly wife needs tea, sympathy and general looking after. Sundays forecast looks hopeful too.
It is sounding like a decent shed frame of at least 8ftx8ft dimension, with a clear plastic pent roof (possibly underlaid with aluminium foil) and thermally lined, preferably with a drop down side, is a hopeful way forward. I can always look at whats available commercially off the shelf and do some hacking.
9’6″ x 9’6″ (3m?) sounds about right I think given the size of that scope – or you would be hanging over the walls. I’ve worked comfortably with a scope and small foldup table in a 9ftx9ft. I am wondering if 8ftx8ft is just a bit too snug. But if I can set the thing up for remote use (30ft away in the lounge) would even 7ftx7ft be enough?
Separate note. Is that a MkIV Fullerscopes mount? They were hefty.
Thats surprising – one of our plastic garden stores does occasionally get condensation. You would think the plastic would have the same problem as the POD. Perhaps its borderline. I think I would take the precaution of lining to some extent – if it doesnt make the whole thing too heavy.
Yeah, some spiders must be very keen astronomers, they gravitate to optics. Rather like the family of earwigs that once took possession of my Fullerscopes MkIV mount….
Has been suggested here that wooden observatories are – at least while maintained – fairly benign environments, but that 8ftx8ft would represent a minimum size. Does that fit in with everyone elses views? I have found a 9ftx9ft shed usable and the circular Skyshed POD quite tight with its 2.4m radius.
Ah, that sounds familiar. A wooden shed I have occasionally used in the past does that too. Everytime you go there you have to spend time clearing webs from the lights and mains sockets.
It was the dryness of that which made me wonder why I put up with the POD’s condensation problem.
I’m thinking 7ftx7ft with a pier mounted NEQ6 and probably a Celestron 11″ RASA (can’t afford a 14″ RASA and mount upgrade) plus something like an SX694 CCD. Am not sure 7ft is big enough, but am not keen to throw away garden – the run off frame area is pretty much dead space in the garden. Also , I want to keep the thing as low profile as possible so it doesnt take over the view from the house – yeah, I’m not making life easy for myself.
Its a long time since I read the Arditti book, but I don’t recall seeing a ROR made of polycarbonate before. Nice. Is the sheet screwed on to the frame or glued? A material that light weight: I wonder if it could be hinged?
I have been wondering about recycled plastic for the roof to minimise the impact of weathering, but its pretty heavy stuff.
Thanks for that.
I have read my copy of Webb’s book several times and generally enjoy it for the style and language rather than anything else. Is that much the same with Smyth?
Its the original focuser.
A Starlight H18 and a Starlight filter wheel.
It didnt happen after we put some tension of the focuser. Besides which, we were fast slewing an awful lot, so the scope would go from near zenith to near horizon in just a couple of minutes.
We just installed a C11 RASA instead. Can’t use filters but it has a much wider field of view.
I’ve used a 10″ Altair RC quite a bit and found that once I got the tension in the focuser sorted out, focus seems to say pretty tight for several hours. We had a couple of instances where it changed abruptly during the night, but that was some time ago now and seemed to occur only with a heavy CCD.
