Uranium235
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Everything posted by Uranium235
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No prob mate, will do!
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Which adaptor are we talking about? My threaded solution or the dovetail adaptor? The advantage of a dovetail over a straight barrel is that it "pulls" itelf tight to the EP holder when you do up the thumbscrews (becuase its a dovetail), whereas the straight barrel adaptor can still "pop" out a bit under the weight of a heavy camera - leading to tilt in the focal plane. If you have one of the spare SW dovetail 1.25" EP adaptors in your bits box (they often come with SW scopes), pop it in and try it - you will see what im on about straight away. Its a pretty cheap adaptor from TS, so worth a punt (even though its designed for their rotation system). Give us a week and I might get one in to test the water as it were.... worst case scenario would be that the thumbscrew holes would need to re-drilled (moved up a bit) if the dovetail is a bit short (hard to see it in the photo).
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All is well then, with FLO you are in good hands. And you might even have some clear sky to practice on
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Youre going to need to get that sheared bit out somehow, if the threads arent wrecked so you can try gripping and turning the sheared bit wearing a rubber glove, or with the eraser end of a pencil. Remember: Righty tighty, lefty loosen (you dont want to send it in further!). Hopefully you should be able to get it out far enough so you can remove it. It looks like you have quite a lot of thread left on your locking screw, so there is probably only a few mm in there. Might be a good idea to smooth off the end the screw with a fine file or some emry paper if its a bit rough. Failing that, send the scope back from whence it came and get a replacement.
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Reason is becuase I was having an awful time trying to get my 383 to calibrate properly a few months ago when I got the Star 71 - the flats were over correcting by a long way (giving bright corners). That was with an average level of 26,000 (1/3 histogram in Artemis), so I backed it off to 20,000 maximum level instead and the problem went away immediately. Ive just checked an old 130pds flat, and that was just under 22k maximum - so its in that genereal ball park area (26k+ is a bit high). Both scopes have a completely different vignetting pattern, so there will be some element of experimentation.
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This is what I mean by a bespoke, all M48 threaded solution (with internally mounted CC and tilt adjustment): Its not the kind of thing you can buy off the shelf, you have to buy the separate components and fit them together yourself (requires a bench drill, taps and small countersunk hex screws). Bonus being it can be fitted to any 2" skywatcher newtonian focuser, so you can chop and change at will - and it opens up threaded collimation, which is far more repeatable and reliable (though you do need to remember to remove the CC first.... otherwise its metal on glass... not good!). However.... there is another way you can have an internally mounted CC (though it has to be the Baader), and that is to get a dovetail pushfit adaptor - which would be much better than the straight barrel versions. This one has a 2" fiilter thread scope side, so that is where you would situate your CC. Reason why I said it needs to be Baader is because you can remove the T thread component, just leaving an M48 cell (which is what is inside my adaptor). http://www.teleskop-express.de/shop/product_info.php/info/p2742_TS-Optics-Adaptor-2--to-T2---low-profile---dovetail.html The only downside to that is its only available in a T2 camera side fitting, so you would need a T2-M48 adaptor to get it to fit your filter wheel (and losing a bit more spacing to play with in the process).
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For dimming your panel, just use a few sheets of copier paper. In regard to avoiding the shutter, your flat length should be at least 8 seconds - which is a bit more conservative than the 6 seconds quoted by Atik - this is especially true when binning. If you are thinking of replacing the thumbscrews, you will have to come up with your own bespoke threaded solution becuase compression rings should be avoided at all costs (they are the devils work!). I had to produce my own adaptor by allen bolting an M48 thread to the pushfit adaptor - that allowed me to mount the Baader CC internally in the drawtube via its M48 thread... and to get the SW CC in there I literally had to hacksaw and file off its collar (only for the brave!... or mad). The backfocus for the 383 is 17.5mm I believe, the mechanical drawing for the camera can be found on the Atik website. In regard to the correct ADU levels, aim on the low side - between 16,000 and 20,000 max ADU (not average). Do not trust the figures given by artemis capture, instead load the test flat into Maxim DL (if you have it) and change information mode to "Area", the maximum ADU value shown there is the one you should be working with. I only found that out after trial and error (yes... lots of error!).
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Clear/Cloudy/Clear/Cloudy etc, etc, etc!
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Should work well enough with a DSLR, its a fairly quick telescope so its quite a good match. Actually, it would be a good deal less complicated becuase the weight of your average DSLR isnt putting much strain on the focuser.
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When taking flats with the 130, use a large lightsource (ie: a big monitor running notepad or Al's virtual lightbox), back it away by about 10 inches and diffuse the light with some copier paper - that will help prevent stray light from bypassing the primary/secondary and going straight up the drawtube. In regard to the CC, try to stay as close to the 55mm spacing as possible as going over that will increase the reduction factor, but increase coma in the far corners. It also helps to have three thumbscrews fitted rather than the standard two, that will help prevent the CC from flapping about in the drawtube under the combined weight of your imaging train (a CC, FW and 383 is a bit heafty).
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Guiding tonite!
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A bit of a lean year for me, two bad winters and a so-so spring and autumn - so not much to choose from really!
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Just spent the night tinkering with this to remove the stars.... very tedious work indeed!
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Something very odd is happening, Ive actually got a telescope outside!
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Erm... I can see little white dots in the sky and no clouds... how odd!
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Enough of the cloud already! Been out just once in the last month.
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Rubbish weather = bake another cake. The challenge for tonight.... lemon drizzle cake =P (very apt given the weather!)
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Rubbish weather = bake another cake. This time its carrot cake with orange flavoured cream cheese topping.... nom nom nom.
