Clarkey

I am following up on this post as my worst fears have been realised. Previously I could consistently guide to 0.6 - 0.7" rms and the mount was pretty stable when guiding - only minor corrections required. Now I am lucky if I can get close to 1" and more often 1.5" or worse. The mount motion is just so erratic. It guides ok for a while then seems to throw a complete wobbler and be all over the place. Since the 'incident' I have opened up the mount and checked for any (obvious) damage and can find none. This mount has just had new bearings throughout and a complete strip-down and rebuild. I have recalibrated and reduced the backlash as much as I can without binding and also done the usual guiding assistant etc. So, the question is - does anyone know what might be causing this random behaviour? The only thing I can think of is that the worm drive has been very slightly bent - but that would be a consistent pattern, which this is not.

A bit late, but here are some individual subs. One flat frame and one image frame. I am seriously considering binning this camera. I tried some more imaging with the same result. What makes it worse is the sensitivity seems so poor. The trouble is, I don't want to sell it if there is something wrong with it (which I suspect), which means I now have a £1000 paper weight. I could sell it and for the money buy another second hand 1600mm pro. At least these work. @ONIKKINENand @tomato - please feel free to have a look at give me your thoughts. Image Frame.fits Flat Frame.fits

I leave all my kit outside all night when imaging so I can't see this being a problem. I do use the 'Rain Alarm' app and I also have a rain sensor, but if the forecast is good, I don't see everything out overnight being a problem. FWIW I actually converted a cheap BBQ cover to a lightweight scope cover, which works quite well. Just taped up the seams.

Wrong thread.

I briefly worked with a dual rig using a mono camera plus a DSLR - just an experiment really to see if it was worth investing in a OSC. Also, one of the scopes was only a doublet so there was a small amount of false colour. If I work out the problems with the OSC camera, I might go back to it at some point... I would say go for it. I think the mono will give that small bit of extra detail and the colour management will be little different to now. You will also get the bonus of NB imaging.

That was just my poor wording. I realise that genuine gradients will not calibrate out with flats. (Although there does seem to be a bad area in one corner of the sensor which rotates with the camera / scope. When it is not so cold, I will try to collimate the RC8 as it is a little bit out and it could be the cause). Yes. I am a stickler for clean filters / lenses etc. My 3 years old 1600mm and the filters for that show virtually no dust. I have cleaned everything but still get some prominent dust motes which will not go away. I am pretty certain these are on the inside of the glass. I am just reluctant to send it back to China or open it up.

I think it is overcorrecting some of the gradients - not the image as a whole. In most case it is not as bad as the horrendous image above. But it is still not correcting correctly. NINA was suggesting an 80 sec flat - I have no idea why. I did not take 80 second flats - I ended up doing them manually to about 1/3 of range. I will try to post some single representative raw frames when I get a chance for people to dissect at their leisure. Thanks for everyone's input so far.

Yes - both. I'm assuming the flat wizard would use the same for both imaging and flats - my offset is currently at 700. Mine is something similar and has worked fine with the other cameras. The histogram is odd in that although using the ZWO fits viewer it looks normal, but in APP and Affinity is very strange. I am guessing the ZWO program stretches and aligns the 3 channels.

I'll have to try this. Not something I have done so far. Do I need to do something similar with the images of just create the flat with the box ticked? Yes. I'm not sure they are too bright - but yes there does seem to be some over-correction. The image above seems particularly bad so I wonder if something else is going on. Even on other images the correction is poor. And yes, I am using the right Bayer pattern, although I think APP works it out anyway. As I said in a previous post, I am actually getting a warning from NINA saying my flats are too dim and suggesting I need 80 second exposures?!

Hi, I'll try to answer some of the questions. Firstly, the green hue I am expecting - its twice as much green as the other colours. This is a screen shot of a flat. The histogram is very odd for an RGB - it has no blue in it. Below is another flat opened in affinity which looks totally different? As for the 'Flats are too dim' - I am completely lost on this one. The problem I usually have is getting the flat panel dim enough. No - but they really show up of the 'corrected' images. This is a corrected image - even worse than the one above: FWIW - I have the inbuilt dew heater and an additional dew heater, so I don't think it is due. I am at a total loss as to what is going on with the camera. Yes - it is stacked and stretched. I appreciate there will be some difference - but not to the extent it is showing. The gradients can be seen on single and stacked flats (don't worry about the very dark patch on some - that is the OAG which needs adjusting. This is a single unstretched or altered flat: No error messages. The gradient removal sort of helps - but it is only masking another issue. The quality of the images does vary - but there are none that are even remotely acceptable. The last image of the original post is the best I have managed.

Up until now, most of my imaging has been done using a mono camera - ZWO 1600mm pro and I have no issues with gradients / processing. I have also used a DSLR in the past. However, over the summer I decided to buy a OSC camera - in this case the Rising Cam IMX571. I have only had 3 nights to try and get any imaging done since the purchase, but what I am getting is awful and useless. I feel there must be a problem with the camera, but it might just be something obvious I am missing. For information, I am using exactly the same set up with the mono camera without any issues. There seems to be three main problems. Firstly, the images have really bad gradients across them. Secondly, the flats are not compensating and actually making everything worse. (There is also a lot of dirt in the camera which however much cleaning I do I cannot remove the dust). The histotgram for the flat is very odd, with three distinct peaks. Thirdly, when I try to take flats, NINA often says that the screen is too dim, even though the light panel is on full brightness - almost like day. In addition to this, in Affinity it opens as an 8 bit image and in Astro pixel processor the flats have a fixed value blue channel. I am at a bit of a loss regarding what is going on. I have updated drivers / firmware where I can, but I still cannot get a decent image. Any guidance regarding what I am doing wrong would be greatly appreciated.

Welcome to SGL. The ES ED127 triplet is a great scope, but as others have said you will need to spend a fair bit on a new mount too. Have a good look through the many 'which scope' threads on SGL and you will get a good idea of the options. As it has been said, AP is a money pit (he says from experience). If you already have a suitable DSLR you can use this, which will certainly keep costs down. The other thing to consider is buying second hand - but make sure it is from a reliable source. You also need to consider what you want to view / image as this will have a bearing on what you need. A large SCT is great for planets, but useless on most nebulae. Similarly, a small refractor would be great for widefield imaging, but poor for planets and most galaxies. Good luck with your journey.

Yes, agreed. However, there are fungal spores everywhere so surface removal is a bit of a thankless task. With regards to the UV, yes, fluorite glass does allow some transmission into the UV shorter wavelengths. I believe the Esprit uses BK7 glass as the non-ED elements. This has very poor transmission below 300nm. Yes, it does depend on thickness - thicker glass moves the wavelengths, and the exact glass properties will vary. In general, for biological disinfection 254nm is the target wavelength to damage DNA / RNA. At this wavelength the transmission is near zero. Given that many fungal spores are very resistant to UV the benefit of a UV light will be negligible.

To save anyone some money who might be thinking of the UVC idea. I might be wrong, but to my knowledge UVC will not pass through glass. (This is why you do not get sunburn sitting in the car). Anything within a glass lens cell will not be affected. FWIW, if you manage to get the atmosphere dry enough using a desiccant, this will probably finish off most things that are likely to grow in the lens cell.

I'm now in a dilemma. Should I be happy that the weather across the rest of the UK is just as pants as it is here, so what I'm putting up with is not that bad. Or should I just be more depressed.😭 The trouble I have is once we get out of winter, there is not enough darkness for imaging. I will keep praying for a long cold spell in the spring. Now where did I put those golf clubs.....

Looking through the guidelog, I would agree with @900SL that changing the cable would be a good starting point. Initially the guide commands were working OK, but for some reason just stopped. This suggests a mechanical or electrical issue rather than software or drivers. Did you try slewing from the PC to see if the mount was responding from any other software? On a separate point, you might want to increase your guiding exposure slightly. At 1s you are likely to be 'chasing the seeing'. Probably 2 - 3 seconds would be better.

Yes you will be. The centre of the RA axis will be pointed at the pole regardless of the mount tilt. If the mount being perfectly level was critical, we would be taking levels to our mounts to get them perfect. The measured RA / DEC might be wrong (hence the goto issue), but the axis will be correct.

Which bit don't you agree with? It is correct that you only need to be approximately level. If you are correctly polar aligned, it should not matter. The only issue with not being level is a single star alignment will lead to inaccurate go-to's. 3 star alignment should remove the problem and give accurate goto's. Tracking should not be affected as you will be on the same rotational axis.

I'm not sure if I am imagining it, but this year seems to have been awful for clear skies - at least since the summer. In August I eventually got round to building my imaging observatory with two pillars and mounts. One for wide field and the other for smaller objects. However, since then I have not managed a single imaging session. I got half a night in about 3 weeks ago, but the seeing was so poor I literally binned the data. Also, I had a serious condensation problem on one of the scopes. I set up my gear this evening as the forecast was promising, but no sooner had I started a sequence it clouded over completely. So due to being this far north and the weather, I have not got a decent imaging session since early May. I think the most annoying part is that there are plenty of others regularly churning out images in other parts of the UK, often not that far away. My concern is that with global warming as it is, this may become the norm. Despite the observatory (and the £3k spent on it), I am seriously considering selling up and taking up golf. (Expensive, frustrating and achieves very little - sound familiar?) At least with golf you can play when it is cloudy. What makes things even worse is the forecast here is regularly a total work of fiction. Often the forecast is for completely clear skies and it is overcast and raining. Perhaps worse is the opposite. Lousy forecast and wake up to clear skies and a frost. Ok. Rant over. Didn't make me feel any better either.

Mine does sometimes and in the same place - obviously a sensor issue. It is OK with dithering and bias though.

I think you could at least double that figure for here. I have managed one imaging session since the end of the summer and the seeing was so bad I binned (literally) all the data. I estimate I get about 2-3 days per month that are useable for imaging, plus a few more that might be OK for visual. I am beginning to feel the observatory was not a good investment of time and money........ By the time I had finished, my PC would be out of date and FITS files would be a thing of the past. 🤣

I don't think you will be disappointed. I was debating the Esprit 100 when the SM90 came out and I got it at the initial reduced price of £1300 so it was a bit of a no brainer to me. My only worry with the Esprit is there are quite a few stories relating to pinched optics in cold weather. There is obviously an issue with the lens cell which can be a problem. I'm not sure how common the problem is though.

The focuser on mine is very good. Most of my other imaging scopes I have changed for Baader Steeltrack but not this one. Nice and smooth R&P with a good rotator and virtually zero backlash. The imaging circle for the SM90 is quoted as being up to APS-C, so ok with an IMX571. I have not tried mine with it - it is set up with the mono kit, but I have no reason to doubt it would be OK. I have had quite a few scopes and this was certainly the best out of the box. I have not needed to modify or adjust anything. Honestly cannot fault it.

Not a real one I'm afraid. Just another incomer. I have been in Penrith for 20 years, but I don't think you are Cumbrian for at least 3 generations😂

I use the 1600mm pro with unmounted 31mm filters - so marginally bigger but probably only a mm or two. According to 'Astronomy Tools' the minimum filter size would be around 26mm. So in theory 1.25 inch should be Ok. If you were interested I'm sure you could ask the question on SGL, there are a few with the SM90. Or check with FLO.