wimvb

No galaxies for a while, so I've pointed my scope at other objects for a change. Here is a nebula in Andromeda. The clouds in this region only have scientific denominators, no common names. Although, the main stars in the image are members of the (very) open cluster Aveni-Hunter 1. The small reflection nebula near the central star (HD 222142) is has the identifier [RK68] 118. The dark nebula has several identifiers: TGU H701, PGCC G110.34-12.65 and similar. Finally, a small planetary nebula near the bottom of the image has identifier PN K 1-20 Anyhow, the image was taken with my usual kit: Skywatcher MN190 on an AZ-EQ6 with ZWO ASI294MM camera Integration time was 4 hours for colour (20 x 4 minutes per channel) and almost 2.5 hours for luminance. The small planetary is interesting. Despite its small size, I believe I managed to capture the white dwarf that is left after the star's collapse.

How high are your washing lines?

That sounds very much like the cold playing tricks. Shrinking metal parts can cause connections to become loose, and most gadgets weren't designed to operate in cold weather. I was one of the early users of the Pegasus FocusCube, and ran into trouble when the device stopped working at temperatures just below zero. The fault turned out the be the USB chip inside the controller that couldn't handle low temperature. Pegasus Astro was very fast in replacing the chip and solving the issue. Now the focuser works flawlessly even at -25 C. Most of the devices that we use and their parts, are intended for indoor use, yet we expect that they perform in extreme conditions.

First off, there is a synscan app (for android) that is very handy when you need to enter your location and time. It's both a time saver and extra insurance that you have the numbers correct. The app includes polar scope reticule. Second, after 2 star alignment, use the synscan all star polar alignment routine. After first polar alignment, park and turn off the mount. Then start from scratch. 2 star alignment should now be much closer. Repeat the polar alignment. Goto should now be very close on each target that is on the same side of the meridian as where you did the 2 star alignment. The first star in your alignment will always be far off, because of possible inaccuracies in the location and time, and (more importantly) because of cone error in your rig. The mount manual has a procedure to reduce cone error. Some cone error won't be a problem, but too much of it is a nuisance. Use a low magnification eyepiece for initial alignment, but use a higher magnification to finetune it. I used two thin copper wires to make a diy reticule out of a 10 or 13 mm eyepiece that came with the scope. Quite easy and well worth spending some time on. It doesn't need to be super accurate, but it will boost consistency. Because tracking is accurate, there is nothing wrong with the mount. But I would turn off the encoders, and avoid releasing the clutches. Use the synscan to slew.

Your back may not agree with you; the EQ6-R is a heavy mount. But it does have a handle for easier lifting.

I once read about a lad who had glued small pieces of a flat mirror to the inside of a satellite dish. He stored it in (his parents') garden shed. Which burned down one sunny day ... Mind where you point that model on a sunny day. 🙂

EQ6-R any day (or night). A friend has one in my obsy where it sits next to my AZ-EQ6. It consistently gives better guiding, occasionly below 0.35", most of the time below 0.5". But it is heavier, so better placed in an observatory. The altitude bolt is tricky, but can easily be replaced. Again, in an observatory this is a non issue. For a mobile setup, I'd probably recommend replacing it.

Do you still have these in Ireland? 😉

I made a cable myself from a RJ12 cable. Not too difficult if you're reasonably handy with a soldering iron. I just followed the drawings in the synscan manual. V2 of the cable had a dither box between, so I could do unguided dithering.

Quite a while back (a few years I believe), there was another thread about unexpected diffraction spikes. At that time the culprit turned out to be a power cable or something. Clearly the definition of light path is a loose one.

I do have a small Teleskop Service refractor with built in corrector/flattener. Bought it last spring and have hardly used it. I wouldn't mind a good quality refractor, and if I now win that million dollars, I will probably get one The MN190 can deliver refractor quality images for a substantially lower price, and still have a decent speed (f/5.3). When I was in the market for a new telescope, I did consider the then new Skywatcher Evostar 120 ED, but decided against it. The MN190 has more aperture for money. Esprit was and still is out of my league, but maybe in the future I will get a large refractor. They are easy to use. But for now, I'm happy with the MakNewt.

😄 The MN190 sings. I just open the roof every clear night.

There is a straight line obstruction perpendicular to the diffraction spike. Look into the ”business end” of your scope/lens and see if there is a straight edge somewhere in the light path. there is also a shadow in your diffraction pattern. Lens clips maybe? A small obstruction at the very edge of the optical elements can be the cause.

Yes, that's the idea. But also, if you bring in the black point for red, it will shift the histogram to the left, aligning the right side edge with that of green and blue

Thank you, Tom.

I don’t use Photoshop or Gimp, but one thing to note about histograms and how the work. histograms show the distribution of intensity levels. The peak is the most common intensity level in the image. In astro images with a background, such as star fields and galaxies, the peak of the histogram indicates the average background level. The width of the histogram is often considered a measure of noise. But if you think of it, a wider histogram means that there are more dark pixels and bright pixels. The thing is, we don’t notice the dark pixels. But we do notice the bright pixels. So, if for example the histogram for the red channel is wider than that for green and blue, there are more bright red pixels than green or blue, and the background will show a red cast. Even though, if you measure the average background, it will be neutral. To get rid of this colour cast, you need to adjust the widest histogram. One way to do is, is by aligning the right hand slope of the histograms. pixinsight has a tool to adjust this type of colour cast. It is called scnr. scnr = subtractive chromatic noise reduction.

Thanks. I have several more obscure objects in the works/planned. But they are a bit closer to home. If the weather plays nice, you will see the results on this forum in a not too distant future.

That is a very big minus for the ASIair. I guess that the app tries to be smart and set the tolerance according to sensor and focal length used. Otherwise long focal lengths wouldn't be possible, and very short focal lengths would run into mount accuracy problems.

Thank you Göran. 1000 mm focal length is something like a "nifty fifty" in daytime photography. Not too wide field, nor too zoomed in. Or as we would say it, "lagom".

Can't you set the accuracy you want? In Ekos, I have set it to 30 arcseconds, or about 32 pixels. I'd imagine that the ASIAir allows something similar

Thanks. I think it is a galaxy cluster, but I couldn't find a reference in Simbad about it. In Aladin (SDSS sky survey), there definitely are some galaxies there. Maybe Nasa's database would give a hit, but I haven't learned to navigate that yet.

At least England would be dry under a roof.

This is my latest project, galaxies and an asterism in Triangulum. The most prominent galaxies are ngc 672 and ic 1727. At the top even edge on galaxy ngc 684. Near the bottom, what looks like an open cluster is actually "just" an asterism; Collinder 21, with just above it galaxy ic 1731. And for the "Easter Egg", right next to ic 1731 is an actual cluster, albeit made up of galaxies rather than stars: [RRB2014] RM J015034.2+271226.1 at roughly 3 billion light years. The data was collected during last week. 200 minutes per channel RGB (10 hrs in total), with my SkyWatcher 190MN and ASI294MM. I had collected luminance, but the quality didn't match the colour information (lack of matching flats), so this is just the RGB data. I extracted L*a*b components in the linear image and deconvoluted the L. Then I combined the L with the colour data and processed as an RGB image.

Just read your post. You should be able to measure if the belt tension is ok. With my AZ-EQ6 (belt drive), I consistently had a 10 s period in my guiding (you need 1 s guiding exposures to see this). I analysed the guide graph and a frequency analysis showed a pronounced peak at 10 s. It turned out to be caused by the belt being to loose. Tightening the belt improved the guiding. The next hurdle was adjusting backlash. I spent two evenings on this. The trick is to take it in small steps (1/32 of a turn of the grub screw), and use the guiding assistant to measure backlash after each adjustment. Also check for binding after each adjustment.

That looks good to me. The proof is in the proverbial pudding, ie a star test. You center on a bright star and defocus to get a doughnut shape. If the hole is centered your scope is collimated.