Stuart1971

Quite happy with this for just 1 hour with my QHY268c and the Optolong L-Extreme filter.. Processed as Ha and OIII, although the RGB processed version looked pretty much identical…

Brighter version

Heart Nebula with Fish Head Nebula, just 1.75 hours on Tuesday night, then clouds rolled in 53 x 2 min Subs, with Optolong L-Extreme filter, with QHY268c and Tak FSQ85

It’s not field rotation, as it’s all over the image in the same direction, it’s as I just said above…our posts crossed, all gone in final image as shown above too….

The coloured streak are the hot pixels from the camera, and as the images moves on the sensor over the period of imaging for a few hours, then when stacked and stars are aligned the hot pixels then form the streaks, but during stacking with all calibration files as you see in the final image above, they have all been taken care of, I use APP for stacking and works really well….

Yes and not even RGB the the L-Xtreme filter is narrowband, Ha and Oiii only…👍🏼

Ok well I think I am getting somewhere at last, 53 x 2 min subs with QHY268c, before clouds rolled in, with the Optolong L-Xtreme filter, wow this filter is good…. Quite pleased with the result from such a small amount of data….. what do you guys think….a bit noisy I know…but needs more data….👍🏼

I think it’s the very corners of my images, so not perfectly flat, centre stars look ok….here is final calibrated image of just 53 x 2 min subs, with the L-Xtreme filter….not bad for such a short amount of data…🤔

This is a highly zoomed in portion of a stacked image but with no calibration frames at all, with QHY268c at -15, just wanted to check the data I had, these were 2 min exposures with the Optolong L-Xtreme filter, and guiding was very good, so what causes these hot pixel streaks, the stars are round…?? Now with 5 min subs with just an LP filter I had none of this, so is it purely down to needing longer subs…?

Sounds like a very productive first light, and I remember the feeling, it’s very satisfying when all goes well…I too noticed last night that I was getting good data of my target on my autofocus subs which are 6 seconds long, and this was down to using the Optolong L-Xtreme filter, why is new to me and first time I used…just wow…and I would highly recommend to anyone with Medium to bad LP, it really does make such a difference to the amount of detail captured… Anyway good luck for future sessions…👍🏼

Absolutely, I think the company is a disgrace, and I am so glad I built my own, as I had a quote from these guys, and was very close to going ahead….lucky escape me thinks….😮👍🏼

Well if he has now seen this I doubt he will reply to any emails…..☹️🤔

With APP, and my QHY268c i shoot at -15, and i use Darks, Flats and dark flats, there is no need for bias as the bias signal is in the dark flats… I have not tried without darks, but the above gives me great results in APP, but the flats and dark flats should be at least a few seconds long, as with my camera if they are too short it can cause issues, so nothing under 2 seconds…

With DEC backlash it’s good to have polar alignment misaligned anything up to 10marc mins, this helps as it then drifts in one direction so you only need to correct on the DEC axis in one direction, this makes any DEC backlash moot, this is a recommendation from PHD2 developers themselves…mine is 4 arc mins off in PA, and I guide in south direction only, as I have 3220ms of DEC backlash… Like me you also have large guide camera pixels, but you BIN it….why ?? that gives a massive almost 15 micron pixel, so with min move set at 0.45 it has to move 7 microns across your pixel before it registers, this then means the imaging camera has already seen the move, and will show in images, you want the guide cam to see the error first and correct, so don’t bin the camera, and reduce min move to about 0.10.

All good…nice set up there….👍🏼 You may be the first to do that on the ASIair, but it’s been done for a long time on Stellarmate and Astroberry systems, which are the same but much cheaper than the ASI version, and work with all makes of cameras…👍🏼

Beautiful scope…but I would consider putting a losmandy dovetail on the bottom of that rather than the vixen type, it will be a lot less prone to flexure and generally more solid, as it’s a good size scope…👍🏼

I asked the guy who wrote EQMOD about why it was recommended not to change the Min Pulse setting and this was his reply… ”You can reduce the min pulse guide width down to 20mS but the problem is it is that this then getting down to a level where any errors in software timing or comms turnaround delays become significant. So you may be able to get shorter pulses but they may not be consistently accurate all of the time. If you're currently at 0.5x you still have some scope to reduce the guiding rate and I would probably go that route first myself’

Ok, so one last question, would all this still be applicable for a guide camera with 3.75 micron pixels, and a guiding scale of 2.18”/pixel…🤔

Thanks for this, this is what I thought was going to be the issue, 0.9x is just far too fast for the guide rate on this mount…the guiding assistant recommended 0.1 for min move…I did try that but still had to really lower the AG setting… I also read in the paperwork for EQMOD that a setting less than 50ms would not work properly…and not to bother adjusting, why does it say this, as what you say makes a lot of sense…🤔

You say.. If you have guide speed set to x0.9 sidereal - that is about 15"/s. 50ms is 1/20 of a second so minimum mount correction can be 15 / 20 = 0.75". so are you saying that 0.75” is too much for a minimum, and why I get overshoot and oscillation on the RA..?? and to “either” lower the guide rate or reduce the minimum pulse, but not both…??

So the fact that I moved the aggressiveness setting down to 15 from the default of 70, this would have only sent 15% of the computed pulse and so compensated a bit, because my guide rate and minimum pulse is too high ..?

Yes I get that, and I will post a log as soon as I can get out and my biggest issue it RA correction going back and fourth, this is with 0.9x guide speed and have now been told by a few EQ8 users that this is way to high and too aggressive, hence going to try 0.5x, to try and stop the oscillation…. ‘I did adjust the aggressiveness right down to 15, and with this I saw figures of 0.65 RMS…

Can you explain on what mechanical issues, the mount is in excellent working order, with albeit backlash on the DEC axis, which doesn’t seem to be an issue with guiding in just one direction, and I was using 0.9x guide speeds, which apparently is too high, so am changing to 0.5x to try…. Also you think my guide set up with 8.6 micron pixels could not be made better…..🤔🤔 So what other mechanical issues am I missing here….??

Backlash in RA is moot, as it’s always traveling in the same direction, same in DEC when guiding in one direction opposite to drift….👍🏼

Backlash on RA….🤔🤔 no that’s not an issue…