DaveS

I am in the process of getting the EPDM on. I have it stuck down to the roof, well, sort of a there are wrinkles in it due to my lack of eye-hand coordination (Almost zero) and really needing two people on a roof that size. Hope it will last until I rebuild the roof in a year or two. Going to have lunch now, as I want to be able to take my time over getting the edge sealant on, otherwise I'll make a pig's ear of that too . Oh, and I have PVA all over my hands, been washing them but I think most will have to wear off.

I had to fudge the sizes of the reinforcement sections, as the roof battens might say 25mm on the Wickes site, but are actually 22mm . Result was, that instead of the 25mm x 3mm wall tube I wanted, I had to order 5 lengths of 20mm square x 2.5mm wall steel tube plus 5 lengths of 20mm x 3mm steel strip as packing, which I cut with an angle grinder.

Some progress today. Managed to get the three remaining reinforcement sections in, though I had to remove the top length of roof cladding and cut a hole in the membrane underneath. Much use of the 4lb club hammer and liberal use of cuss words. There is now much less droop in the roof. Also done some fiddly easing around tight areas. Hoping now for the roof panels to dry out enough that I can get the EPDM on tomorrow. I now have a multi-way combination ladder that can fold out into a platform 1.2 metres high by 2 and a bit metres long, enough that I can work on the whole length of a side without having to move a ladder.

No, the Bayer filter is a physical layer of RGB filters over the photosites.

I have a full set of Astrodon 3nm in 1.25", bought at the end of 2014 when they were "0nly" £385 each, now they've gone beyond silly money into stratospheric insanity. Still brilliant though if you can afford them.

If you have any thoughts at all regarding imaging, then get This book and read it at least twice before spending any more money, it could save you from haring down an expensive blind alley. Steve is a mod on here aka "steppenwolf".

OK, I should have been more explicit. My obsy is nominally 2.2 x 2.2 metres outside, so allowing for the wall studs at 95 mm thickness, that means about 2 x 2 metres inside. Which is just enough room for the 'scope, and for me to squeeze round it during setup. If I was visual rather than imaging I would want a bit more, which is why I said 2.5 metre square. I think you *could* get way with a smaller footprint if you had a more compact 'scope than my ODK12. looking at your plans, I think I would endeavour to make the platform / gallery affair a touch bigger else you might find yourself squashed.

The obsy I'm building is 2 metre inside dimension, but it's imaging only and just large enough for me to squeeze around the OTA. For visual I'd be inclined to go larger, maybe 2.5 metre square. OK, it's a big 'scope on a big mount, so perhaps for a smaller 'scope on a lighter mount 2 metre or so might do.

Disadvantage would be that the 3nm H-alpha will exclude the [NII] line which otherwise would add signal to the HII. Of course, you may want to separate the two in order to get a purer HII signal. Chroma don't manufacture a 3nm [NII] filter, though Astrodon do, and should work with the Chroma. But unless you are devoted to imaging Planetary Nebulae I have found [NII] to be of questionable value. Chroma also spec their 3nm filters for F ratios above 4, below that they recommend the 5 nm due to spectral shift. Edit: 3nm is more resistant to that other source of LP that we all have to deal with, namely the Moon, and could give you a few more night imaging with the moon up.

Thanks for the suggestions. My tentative plans are to get the reinforcement sections in soon-ish, but leave this project until next year. At which point I hope to have built the imaging box around the platform telescope, taking note of all the suggestions in this thread so far. What I learn from doing that will be fed back into rebuilding the roof on the obsy, which will put it out of action while it's being done.

Not at all, happy for any suggestions. Two of the hold-down blocks have been replaced, just a matter of finding time in between doing the other obsy work to do the other two. They have been cut ready, now to fit them. We don't get much snow here, last year it was just a dusting, and no snowfall this winter. The roof is, as you say, much too light. I should have had a look back at my original plans which *did* call for heavier timbers when I was putting the orders in to Wickes. I was also trying to keep the height below 2.5 metres for the "Permitted Development" rules. I think I can use 45 x 70mm beams on end. Will investigate the geometry.

OK, then that should be fine, though I hope it has USB3 to handle those huge files. The 6200 cameras bin after download in software, as I think the on-chip firmware is the same as the colour one which bins every other pixel.

3 nm filters won't let less of the wanted light through unless their peak transmission is lower, Astrodon and Chroma both quote above 90%. Myself, unless you really want [NII], which is really a PN emission line, then I would go for Chroma as they are significantly less expensive while being just as good.

For 135 format you will need 50mm unmounted filters as 2" ones could well vignette badly. You will definitely need a more powerful computer to handle those files in any sensible time, I would be spec'ing a tower with a Ryzen 12 core and at least 32 gig ram, plus a few TB of SSD or better M2 storage.

Also available Here. *scratches head* If your location says Suffolk, why were you looking at US sites?

Neither do I really as I do a lot of SHO narrow-band, and trying to get real SHO out of an OSC involves too much of a fudge. Which is why I'm really hoping for a mono version of the QHY 268, or ASI 2600 (Prefer the QHY though).

QHY 128C

Fuji GFX?

I have to admit that the latest crop of CMOS OSC cameras have me in a quandary. I'm seeing brilliant RGB images but I also like doing full SHO NB imaging of emission nebulae which would be a bit of a kludge, as the HII and [SII] would both only use 1/4 of the pixels, while [OIII] might use 2/3, depending on the CFA spectral response. I'm also not 100% sure about the current tri-band filters with both H-beta and [OIII] under one band. Perhaps the answer is a dual rig. If QHY *do* release a mono version of the 286, then two "identical" 'scopes, one with the colour version, and the other with mono and filter wheel might be interesting. That would also make it possible to add NB to RGB, eg for adding HII to a galaxy image. Dunno, waffling a bit as I'm thinking aloud.

Very light, 25x38mm nominal, so I have some steel coming tomorrow. When I rebuild I'll use the 45x70mm timber that I used for the roof bearers, which may get an upgrade too.

Very nice. The forum software won't display TIFFs, so best to post JPEG, or PNG if you're feeling extravagant. I'd like to know the suburb that has Bortle 4 skies! I had to move to semi-rural Dorset to get Bortle 4 (Actually nearer Bortle 3)

Don't make your door too low. I spec'd mine to be high enough that I could walk through without having to duck, as I knew that otherwise I'd give myself a clonk on the head, especially leaving it at night. I've also run a string of red LEDs around the walls for lighting. And for heaven's sake, don't make your rafters too light. I did and now I'm having to reinforce them as a stop-gap before a rebuild next year.

I've been up that long river place looking at blades that might work with my saw (3800 rpm, 305mm saw dia) and found This. Their search is pretty dismal, turning up loads of irrelevant stuff, even with key words.

Thanks Dave. I will have to check, but I think my saw is spec'd for wood only as it's single speed. I think metal cutting saws need to be variable speed?

That looks similar to the arrangement that Sara (Swag72)'s builders used when she had her obsy reconfigured. Unfortunately I am, at present, without a workshop as such and without engineering tools. I can probably work something out with wood. As things stand the 3 metre long rack is attached to a 3 metre long wood bearer that carries one side of the roof and runs through an opening in the rear wall, and the opposite bearer fits into a pocket in the same wall. The rack motor will stop the roof from rolling off of its own accord.