Seelive

Brings to mind a quote that I've read somewhere... "I'd rather be optimistic and wrong rather than being pessimistic and right".

I don't know if the ASIAIR PRO uses DC-DC converters to provide regulated 12V outputs. The user guide warns that continual use at a low input voltage could case the case temperature to rise to 70C which would suggest that it does, but the easiest way to check is to see if the 12V outputs track the input voltage or they remain fixed at 12V independent of the input supply. If the remain fixed, indicating DC-DC converters are used, I would not recommend paralleling the 12V outputs. At best it's unlikely they will share the current evenly, at worst it could damage the unit.

Play with it indoors if you can so that the handset and mount operation becomes second nature hence avoiding the need to search through the instruction manual to find out how to do something rather than actually using the kit first time out.

Apart from numerous astronomy books dating from the late 60's, I've still got my Johnson postcard enlarger (#1 I think -for 120 size film) dating from about 1969 that I used when I first started developing and printing my astrophotos. It now lives in the loft next to the hi-fi system and all the other stuff from my early days 😆. There should also be an Astronomical Equipment (Luton) 4" f8 mirror and flat from my first homemade telescope that I built around the same time but I've not seen that for a lot of years, it's probably at the bottom of a box.

Processed using IRIS with possibly one of the shortest workflows I've ever used: Equalise histograms and apply selective Gaussian filter. Blend RGB (R = ADD_MAX[0.67S, 0.33H, 0.00O OR 1.00S]; G = ADD_MAX[0.13S, 0.43H, 0.33O OR 1.00S; B = ADD_MAX[0.00S, 0.17H, 0.67O OR 1.00S]) Apply luminance ( L = H) ASINH colour stretch, adjust saturation and sharpen The IRIS ADD_MAX is probably equivalent to the PS LIGHTEN and was used to enhance the S regions in the final image.

The stacking software doesn't always give the correct colour balance in the stacked image and removing part of the spectrum won't particularly help in the single image. The colour balance normally needs to be corrected in post processing and even with the IDAS D2 filter you should still be able to achieve a reasonable colour balance.

Just noticed that you're not actually guiding (I should read all the thread before replying!) so I agree that it will be due to polar misalignment drift over your 80s exposure time. Look at the single images and you should see roughly the same drift in each of them. Fortunately the drift wasn't significant so DSS still 'saw' them as stars and didn't reject all the images when stacking. What stacking method did you use? When not guiding and it results in a small amount of trailing, then using the Sigma-Kappa stacking method with a low value of Sigma (say 2 or lower) can help in restoring round stars in the final image.

Guiding will (hopefully) remove any star trailing due to polar (mis-)alignment but any polar misalignment will also result in image rotation as well as shift between the images. The degree of image rotation and image shift will depend upon the magnitude of the polar misalignment and the offset of the guide star from the true image centre. The star elongation doesn't appear to be rotating about a fixed point but also doesn't appear to be completely linear over the entire image suggesting that some other optical aberration may be coming into play?

My Canon battery usually lasts about 2 hours so I use 2, and by the time the second is flat, the first has had time to recharge so I can generally go on for as long as I want using just the 2. Most of the battery drain occurs when using liveview so I try to keep that to a minimum (mainly just for focusing). And I would guess that the battery drain is higher when processing and storing the images rather than during the exposures, so lots of short exposures may drain the battery quicker than fewer long exposures? The temperature also makes quite a significant difference on battery life. On a cold winters evening I may only get 1 1/2 hrs whereas on a warm summer evening can get 2 1/2 hrs.

Sounds like something has been overtightend if the screwheads have deformed the back of the secondary holder.

I don't think that a few degrees out of level would make any significant effect on the mounts stability. Having said that, I always 'level' mine using a spirit level on the eyepiece tray (so it isn't necessarily truely level), hence, along with using permanent marks on the ground for the tripod legs, it means that after the first polar alignment, Polaris is always close to the required position so I don't need to make significant changes to the mount altitude and azimuth adjustment screws in order to polar align.

Unfortunately it isn't, they were the 3 concluding matches from the 'abandoned' 2020 tournament back in March. Turned out to be a great finish though, going down to the last match.

Is far as I'm aware, despite the apparent lack of aberrations, they still suffer from a strong field curvature so a field flattener will still be required for imaging.

I would guess that the secondary mirror is particularly problematic in an open tube reflector as it hasn't got the 'natural' dew shield formed by the telescope tube. I have heard of secondary mirror dew heaters but it's not something I've ever needed to worry about, and I'm sure their are many people on here that could advise you on a solution.

Condensation forms when the temperature of a surface falls below the air dew point temperature (which normally results from thermal radiation by the surface). Leaving the scope out to 'cool' (which is the right thing to do for 'seeing' reasons) therefore means that the mirror temperatures will be nearer to the dew point before you even start observing! As soon as you uncover it, it won't belong before condensation starts to form unless you take other precautions.

Hmm, Skywatcher electronics reliability?

Is the intention to cool the air within the box surrounding the camera or is their some thermal path between the camera and the peltier cooler?

A M3 grub screw should have a 1.5mm hex socket. Unfortunately the quality of the screws do not seem to be that good and the size of the socket seems to vary. Two of mine were OK with a 1.5mm hex key but the other one needed a 1/16" imperial hex key (1.59mm) - but it also depends upon the quality of the hex keys used, they also are not always that accurate in the smaller sizes. The grub screws that were fitted were cone pointed so they 'dig' into the graticule holder. I replaced them with decent quality M3 x 3 cup point grub screws. When I mentioned about the graticule alignment I wasn't refering to the orientation of the graticule, that can simply be corrected so that 12 o'clock and 6 o'clock are vertical by rotating the RA axis before polar aligning. I was referring to the fact that the graticule was not correctly centred. Their are plenty of videos on the net on how to do it. Fortunately it can be done in daylight - I used the tip of a distant pylon so that it remained perfectly on the clock circle as the RA axis was rotated through 360 deg.

Well I consider them all to be dual band but with differing widths of the two pass bands. I have never used one as I image using an unmodified DSLR. I suspect they will be OK with astro cameras and modified DSLRs, but an unmodified DSLR has little response to Ha so I suspect you would just end up with green only images. I purchased an IDAS D2 clip-in filter for my Canon at the beginning of this year with high expectations from what I had read. In response to another query about filters a few of weeks ago, I posted a couple of wide angle images of Orion taken soon after I had received it, both with the filter and without it for comparison (see https://stargazerslounge.com/topic/364513-light-pollution-filters/). With the 50 mm lens I had used, I found it gave unwanted fan shaped aberrations around the brighter stars , so it has stayed in its case ever since. It may work better with longer focal length lenses but to be honest I find easier to correct the images for the light pollution rather than trying to colour balance the image to make-up for the missing parts of the spectrum.

Unfortunately, unlike the old orange low pressure sodium lights that only omit in a very narrow bandwidth which are easily removed by filters such as the IDAS D2, LED lighting is much more broadband, emitting over a wide range of wavelengths. Whilst 'light pollution' filters such as the IDAS D2 will help somewhat, the only real solution is probably narrow band filters.

A very quick process just to see what's there. Glad to see I'm not the only one to suffer from light pollution gradients, I'm not sure I've removed it completely but I wasn't looking for perfection. Apart from from the dust bunnies, their appears to be a green 'smudge' between Alcyone and Atlas/Pleione that may prove difficult to remove. And thanks for letting me have a quick play with your data.

I had some problems to so I imported it into DSS then saved it as a 16 bit TIF. Seemed OK then.

The numbers quoted in that article are based upon using emulsion film, for example to assumes an error of 30um as being accepable. With todays large CMOS sensors, an accuracy 10 times better would probably be required. But the maths are (mostly) valid and the gist of it is that any misalignment between the imaged target and the guide star will result in some field rotation of the image. How much depends upon the accuracy of the polar alignment, the amount of misalignment, the declination of the target, the focal length of the imaging system, the exposure time etc etc. The polar alignment accuracies assumed in the article are generally much worse than those that can now be readily be achieved, and who needs to have 60 minute exposures these days? My imaging system and guide scope are not perfectly aligned and PHD2 always seems to pick a guide star near the field edge of the guide camera but I've never (yet) noticed a problem. If you don't get a problem then everything is fine, but if you do, then you at least may have an answer to the possible cause 😆

I also use homemade dew bands with a homemade controller (the commercial ones seem vastly overpriced for what they are). Normally the controls are set between 30% and 50% but there have been a few very damp nights when it's been necessary to wind them up to 100%. OK, I suppose I could leave it at 100% all the time, but to me it just doesn't seem right unnecessarily heating up the lens beyond what's actually required.

I use 50mm, 100mm, 200mm and 400mm lenses for all my astrophotography images but they are always mounted on a driven equatorial mount (together with a guidescope when using the 400mm).