tooth_dr

It does a good job, but at 1200mm on a small size chip, the prom drifts a bit and requires periodic nudging.

Are these images I took useful as examples? Same camera, same night, one with 250mm and one with 80mm scope?

Yes indeed! If only there was solar autoguider that didnt cost £500+ for an EQ mount. Would it be possible to mount a solarquest tracker on a wedge?

Would there be significant cropping?

Could you post a start and end image Dave, say with a three hour gap? I’m considering one but this put me off.

I don’t know, but wouldn’t the limb rotate too if imaging a prom?

Very good Geof. That’s definitely a significant improvement

I have been trying solar time lapses recently, and agree that it’s pretty labour intensive! Good start so far. I had considered a solar quest mount but I was concerned about rotation over long time lapses as it’s an Alt-Az mount.

There is a lot of detail, great job on the processing! It possibly has a slight magenta cast to it? NGC4217 is the big edge on galaxy on the right side at the corner. NGC4226 is the little one at 8 o’clock relative to NGC4217

I use a 290mm and it’s t thread so fits my tile adapter ok. Can’t you get a t to c adapter? Back focus shouldnt be a problem.

It’s M94, must not be that good though if you don’t recognise it 😂😂

I'm hoping to offset my filter focus positions using a basic autofocuser. I agree, I normally 'aim' to sort of to get green in focus, I think in this case I worked with red. It's an ED80 so a basic doublet, with blue bloating. I was surprised at the green too, but maybe something occurred locally to some of the subs, be it temp change or whatever. If this was a final RGB image, I dont think it would be passable, but it seems to do the job as a colour layer.

Interesting as I'm working through the same process. I think it does matter to some extent, but depends how far out the focus is. In my recent images the RGB filters werent refocused, and the final images are ok, because the luminance was well focused. But I did notice that the stars were large and therefore required much more work, something that I struggled with. You can see the difference in focus below, but it still produced an image. The green focus is definitely off, and i think the blue is combination of CA and bad focus, but less so that green.

I have just watched the video on BL, thanks for that, explained everything. My sticking point was trying to figure out the exact backlash. This isnt necessary. I have finally got my head around it. I will not bore you with the explanation, but now that I've considered it with various sketches, etc, I understand how this works (he says) Just for amusement here are my working out 😂

I worked out 10 using the instructions in SGPro - i think the method was getting focus with a mask first then moving out to get an HFR x4 bigger and working the step size out from that. The Epsilon the only scope I need to get this working. Thanks for the heads up on the videos, will look now. Does SPro do a second adjustment to get to the optimal position, after the over shoot to take up the backlash, as the first position wouldnt be correct?

Right, so it moves past the point by the backlash compensation eg 10 steps, and then back those ten steps, so that we will be short of the optimal point by X. It then takes an image, calculates the HFR, and based on the graph, it works out the number of steps need to get it to the optimal HFR? Is that how it works? I like to understand how stuff works so I can set it up and know what it's doing!!

Thanks very much Olly for the input. First - I will try that, possibly using the High Pass filter? or is there another preferred method? Second - I had collected some Ha, as I had read about the jet, but the data was rubbish so I didnt use it. Now I regret spending three nights since then on NGC7000 instead of getting Ha on M106.

That made me LOL. That is a really impressive result, and it does look like something straight out of JPL. Look forward to the resulting images and mandatory comparison shots.

Thanks Dave, it has been a while since I used the Epsilon, so I dont remember the step sizes, but it may be 10 steps (from above chart) - does that seem right?

I have one stepper and one DC motor. The stepper motor is on the epsilon so i was hoping to get the autofocus function working accurately, as the CFZ is small at F2.8. The DC focuser is on the ED80, and really just want to use that for simple offsets, to get closer to focus when I change filters as current I dont focus at all between filters. I guess if I dont get the backlash sorted in it then it's no big deal, as long as I take up the backlash and always offset the filters in the same direction ie inwards. My head is telling me that unless you know how much the backlash is, then how can you reproduce the position following an autofocus routine? I understand that the backlash compensation has to be larger than the backlash, so that you go past your point and take up the slack, but surely the number of steps of backlash needs to be exacting, or how would you ever get back to the position that the focuser determined? Am I over thinking this? Here is an example from my epsilon, a screenshot I saved in December. In this instance the curve looks good, but it didnt get back to a good focus point so I manually intervened afterwards. I also have since sent my Hitec Astro MHP v3 back to HA, and they replaced the internals to upgrade the size of steps, from 12 to 2um. This was important, as I believe the CFZ of the epsilon is 10um. Does SGPro need to know the exact amount of backlash? If not how does it work around this during autofocusing. In this example my focuser goes from 860 to 800, assuming from OUT to IN, and determines that position 828 is the optimal focus point. At the end of the run the focuser then moves back out 28 steps to what is position 828. But changing the focuser direction means there is some slack to take up first. This uses X amount of steps of the inward offset of 28 steps, so the new actual position is 28-X relative to 800. If X is known then the focuser could move the additional X steps and end up exactly where it should. How does SGPro work if it doesnt know X?

I know What I meant was, even if I had the most expensive filters eg chroma or astrodons, it's my scope and it glass that's not corrected, and therefore doesnt matter if the filters are parfocal ar not, I'll still have to deal with the backlash. I'll have to do the measurements as you described.

Nice improvisation 👍🏼 Unfortunately it’s not the filters but the scope in my case.

Really nice set of images.

I havent submitted anything to Astrobin for a long time, and I did put some images on yesterday, and to my surprise @AdamJ has just informed me that both his and mine are 'top picks'. I dont follow Astrobin, so this may not mean anything, but it's still nice to share the images, and that other folks are looking at this stuff from all over the globe. https://www.astrobin.com/explore/top-picks/

Thanks for that heads up, I'll stop being pedantic 😆