Stub Mandrel

I prefer this to my close up image, it's a stack of 99 4-second exposures using a nice Zeiss 135mm lens. I deliberately left the gradient in

I've got and 1100D, astromodded, that I use for wide angle imaging, meteor hunting etc. I dind't do the mod myself and like the 450D I did do, it hasn't had a spacer or extra filter put in. I fancy using it for some ordinary photography as well, so I'd like to add the sensor spacers or an aftermarket filter to restore autofocus Can anyone recommend a filter that fits over the sensor that won't ruin the Ha response and/or tell me the thickness of spacer I need to add?

Have Have you tried adjusting the focuser tilt?

Last night's data. 12 5 minute subs each of Ha, OIII and SII. ED66, OVO flattener and ASI1600, Baader 7nm filters.

Looked great in my Celestron Nature 8x42 bins last night. I saw M32 near m31 with them as well.

Certainly too big for a 400mm scope! I won;'t relate all the problems I had but worst of all was forgetting I needed an extra spaced between the EFW and the flattener. Turns out my Coma Corrector one doesn't fit so hopefully I can print a stop gap... but somehow I need to find my 123mm lens!

That's a very long focal length for Alt-Az imaging... might be some sort of record!

Saturday night's subs, afflicted by the curse. Previously this has been put down to walking noise (gradual drift of the images across the sensor) but I am convinced its caused by thin cloud. Dithering is often suggested as a cure. I am convinced it can't drift as the first and last subs differ in position by only about a quarter of the length of the streaks. I haven't seen it with the ASI1600 before, and whatever the cause it seems always to be associated with poor transparency. Still the jury is out.

I will be interested to see what difference 16-bits make under UK skies.

Lots of really nice Neowise images n here! I had given up on a decent comet! I can't see the horizon from my garden, so after setting up a final run I walked about a quarter of a mile to a nice spot by a lake with my bridge camera and a tripod. Was surprised to find the comet so easily, and for it to have an obvious tail! I tried various things with my bridge camera. Luckily it has full manual overide including focus, but the longest exposure of 8 seconds gave a blur, but I managed some shots using different modes, 1 second is enough at ISO 800 even at ~1000mm equivalent. These are stack jpegs, one is just three frames, two is six, stacked manually. The last one is eleven frames in high ISO mono mode, stacked in DSS. Stretched further the noise becomes overwhelming. Hope to have another go with proper astro gear!

I managed a test last night, this is an edit of my post in the 'what are you doing tonight' thread after sleeping on it. Main conclusion- too much stiction on the dob part, I need to make it smoother! Not really an issue with the platform, I think I need to dose it with silicon polish at the very least. It moves in jumps and the minimum AZ move is often nearly a full FOV at ~30mm and getting a target centred at 5mm took forever! Alt is much better but not perfect, although if unbalanced it can move on its own. As for the platform, PA was easy, at least to the suggested approach of getting Polaris in the finder and adjusting until it stayed still during a slew. The polar angle must be pretty accurate as I just set everything level and the task was setting it due north. Errors were rapidly apparent so a button to stop the slew early will be welcome. My finder's cross hairs come out at 45 degrees but that didn't make the process difficult. Better PA could be achieved with a polarscope in the finder holder and getting Polaris to travel around the circle. Getting the track rate was hard. A first everything drifted off top left regardless of speed. This made me think it was running too slow. I reduced the delay down to about 15ms until the stars definitely went off the right side pretty sharpish. I then increased the delay, and eventually settled on about 64 milliseconds delay by the time clouds came in, which isn't bad given the estimate was ~68 and expected to need to speed up to allow for compression of the roller. I think the earlier problem was using Lyra which was very high and I suspect a combination of PA error and an unbalanced scope slowly moving in ALT when near vertical. It was easiest to judge movement using small stars near the edge of the FOV rather than bright ones at the centre. Next time I will use a 25mm plossl with cross hairs. Incidentally I used a Szentmartoni EP made according to a recipe on SGL that uses three small binocular objectives for about 33mm. As promised it was sharp to the edge and comfortable to use! I changed to a Skywatcher UWA 5mm to 'fine tune' the tracking rate. the sky wasn't very dark, but I went back and (just) split the double double at 300X - seeing wasn't brilliant, but it seemed to be keeping in place even at that magnification, certainly long enough for planetary imaging. Changes needed: I will wire the disabled reset button on the shield across the end limit switch. This will provide a way of interrupting a polar alignment slew, as initial drift is obvious in a couple of seconds, you don't need to wait for a full slew. I will round the default track speeds 0.1ms and keep the adjustment step of 0.1ms. The 0.1ms seems fine enough and it's annoying that all the readouts are not round numbers - and no point reading the delay to finer resolution than the adjustment. I may change the step to 0.05ms, at the expense of slowing down the tuning process a little. Although up to speed up tracking and down to slow it seemed logical, as up increases the delay and vice versa. It's confusing to press up and see a number decrease. The debounce period for the buttons is too long, as are some of the 'confirmation delays' of 1s. I will reduce both. The 'nudge RA' increment was WAY too aggressive, the briefest of presses and the view changes completely. A remote handset might be a useful addition, perhaps with a reduced set of controls. Mechanically, everything worked fine with the platform. Balance is great and I didn't even bother with a nut on the pivot bolt for the dob, so worth considering a plain pin instead. There is some wobble when moving the scope, but it isn't excessive and I didn't notice any when hands-off. Main beef is with the dob itself, I must find a way of reducing 'stiction' and counter-intuitively locking the alt movement. But my brain is already thinking of ways to add steppers and belt drive to ALT and AZ - perhaps for 2021!

Good, but could have been 20-30 minutes shorter!

Oh Oh... Wimbledon. They'll probably repeat 2019 and cut Horizon off halfway through...

Could also be collimation/alignment as well as not enough spacing for the corrector. Download the trial of CCD inspector and see what it says. Of course the risk is you will want to buy it...

I agonised for over a year. I don't regret going for the ASI1600MM.

Their website is promising a new batch of ASI1600MM - in May 2021!

People don't normally use a diagonal with a Newt, it's function is to make the viewing position more convenient. A Newt's view is rotated 180 degrees, not flipped, so just turn your star atlas upside down.

Hopefully coming to Cura soon! Chris - is there no holding you back? 🙂

I noticed it applies to hammers a couple of months back. Reminded me to post a puzzler I wrote about it in another forum.

A middle way is to buy a mirror set and then build a scope around it, that way you can have exactly the scope you want without the years of angst finishing a huge mirror!

A play with curves could brighten that up and keep the sky background dark and make it look even nicer.

Yes - I mean Arduino Sketch rather than sketch drawing 🙂

I will be putting all the STLs and the sketch on my website soon, I'll drop a link here when I have, but I want to do a proper test before I do in case any adjustments are needed. I also need to draw the finished dimensions of the two wooden panels as accurate locations are important.

That unshielded bearing is annoying me...

52° 78', but I made the platform for 52 degrees as I am likely to be using it further south. It has a few degrees of adjustment built in.