wimvb

Thanks. I don’t have filters for solar imaging, but very likely I will have opportunity to catch noctilucent clouds. Just not with the MakNewt.

Thanks, Alan. I thought this might convince you. Go for it!

Thanks Göran. If the weather plays nice sometime during the coming two weeks, I can probably squeeze in a cluster or two. But after that I’ll pack away the scope and roll in the insulation.

If you have backlash, you need to add that to any dither pulse. Otherwise dithering has very little effect.

The general recommendation is to dither at least 12 pixels. If you align the raw subs (without calibration) and stack them without pixel rejection, you should see a random pattern in the hot pixels. If ototh, hot pixels are in more or less a straight line, then your dither steps are too small.

Astro darkness ended thursday night up here, but it's still reasonably dark för an hour or two each night. With the moon out of the way, I could catch a few hours on the Whirlpool galaxy, M51. I had to reshoot the blue channel because of high cloud which made the combined image look like it came straight out of a low quality refractor, with a lot of blue bloat around the stars. In total I captured about 6 hours worth of data, equally divided between L, Ha and RGB. As always, captured with my 190MN and ASI294MM. To blend the Ha with the red and luminance, I used Vicent Peris' red continuum subtraction technique. One thing that occurred to me when processing this image is that there is more Ha in the arm nearest M51B (the smaller galaxy above the large spiral) than on the opposite side of the galaxy's centre. This makes sense, because the gravitational interaction causes Ha clouds to concentrate and stars to form.

Very nice image. Not to disappoint you, but for anyone doing AP in that galaxy, the Milky Way will be hidden behind their own galaxy's dust, much like IC 342. Unless they live on a planet on the very edge of their galaxy, that is.

One method that I've seen involves removing the secondary and marking a spot exactly opposite the centre of the focuser. Then with either a sight tube or a laser, you line up the centre of the focuser with that spot. This should square the focuser tube. Next you reinstall the secondary, making sure that the gap between the holder and the secondary is parallell (in your drawing it's not). Measure from the tube to the centerscrew of the secondary along all spider vanes, and make all distances equal. Any offset that is needed is usually built into the secondary already. Ie, it is probably glued in place with an offset. But you might test my second idea (rotating the tube in its rings) first. It seems a lot easier.

One other thought. If you point at that faraway church and then, instead of rotating RA, you rotate the tube in its rings, what cone error do you get? If you get any, shouldn't that be an indication of the optical axis not being aligned with the tube centerline?

That looks very far off. When I tried to align the finder scope of my then new 150pds, I couldn't get it aligned with the main scope, no matter what I tried. For a few weeks I lived with it, and at one point was about to return it to the vendor. But then I checked collimation, and found out that it was miles out. Once I had the scope collimated, aligning the finder was a breeze. Moral of the story: revisit the collimation. With a Newtonian telescope, the optics don't have to be aligned with the centerline of the tube, and you can still get a good star field. The entire optical path may be tilted, including the focuser. If so, you are trying to compensate for that by moving the tube, while you should be moving the optics. You may need to start by taking the secondary out and make sure that the focuser sits square on the tube.

A bit late to the party here. I'm not convinced that what we see here is walking noise. The lines are all the way and vertical, which imo, is a sign of the camera's read pattern. A 15 s exposure time is very short, so the read pattern may very well show. But there is a very easy test that can decide. Flip (blink) between the first and last unaligned subexposures. If the images are offset in the same direction as the lines, then it's walking noise. But if the two images are offset in another direction, then what you see here is read noise. You can also examine the pattern of stretched, stacked bias frames. These show either a vertical or horizontal read pattern. The dark shadows are caused by dust motes, and you need flats to remove them. Dithering with a dslr camera is highly recommended. This is easiest done with a guiding program, but there are a few ways to achieve dithering without guiding. One way is to do it manually. (Been there, done that, invested in a guiding setup after one season.)

No, others use them with good results. It should also keep its resale value if you decide to invest in an astro camera. But a dslr has a 45 mm flange to sensor distance, the T-adaptor has a 10 mm thickness. Your flattener probably has an optimal distance to sensor of 55 mm (most flatteners do). This means that you can't put anything between the camera and flattener without introducing star errors. But you still need to focus on something distant, be it the moon or a high building, including a high mast of sorts.

For your budget and the requirement of a portable setup, look at the eq3 pro, eq35 or the newest version of star adventurer GTi, possibly the eq5. That should swallow 1/3 to 1/2 your budget. The Williams optics will take another 1/3 to 1/2 of your budget. For camera I suggest you use your dslr. If you still have 1/3 left, use that for a simple guiding setup, a small guide scope and asi 290mm mini camera.

Focusing on the moon will get you close and is an excellent diagnostic tool. If you can't see any stars, a Bahtinov mask is all but useless. But once you have decent focus, and can see stars, the Bahtinov mask for focusing is hard to beat. For a beginner, it's best to adhere to the KISS principle.

Thanks, Rodd. I couldn't find a reference to a supernova remnant either. Don't know where Kstars got its information. Anyway, the title is there, and I leave it. Otherwise this discussion thread seems odd.

Have you read this? https://wolfcreek.space/index.php/2020/03/25/eq8-r-pro-gear-backlash-adjustment/

The moon is still too bright anyway. And probably too close by.

I thought too that it is an emission nebula, but Kstars has ic 1396A and ic 1396B listed as supernova remnants. According to simbad, ic 1396 is an open cluster and the Elephant Trunk Nebula (IC 1396A, LBN 452, etc) a molecular cloud. IC 1396B (LBN 451, etc) is also a molecular cloud.

Yesterday night we had unexpected clear skies, albeit with a full moon. Astro season is drawing to a close here in Scandinavia, and we only have about 3 hours of darkness at the moment. In two weeks, even that will be gone. After midnight, the Milky Way became visible above my observatory walls and I shot 100 minutes of Ha on the Elephant Trunk, ic 1396. RGB to add colour to the stars and create more depth, will have to wait until August. Gear: SW 190MN with ASI294MM on AZ-EQ6, Baader 7 nm Ha filter 25 x 4 minutes exposures, processed in PixInsight.

Magnitudes are funny things. I get the following: Leo I: 10.0 (Simbad), 11.2 (Wikipedia) Leo II (Leo B): 12.0 (Simbad), 12.6 (Wikipedia) Leo III (Leo A): 13.26 (Simbad), 12.9 (Wikipedia) M 81: 6.94 (Simbad and Wikipedia)

@symmetal I had a stab at Leo II yesterday, despite the full moon. I collected 9x4 minutes R and 5x4 minutes GB, each. I think the Blue was a waste of time, but when I combined all 19 subs to create a fake Lum master, I could just about discern the galaxy with a super stretch. Unfortunately astro darkness will be gone with the moon, so I can’t collect more data until next galaxy season. Perhaps you can still catch enough data before summer.

Excellent rework. Which image processing program do you use. Stretching the three masters before combination seems odd, but maybe necessary in some program?

”In your face”. At 330 000 ly distant and with a diameter of 100 000 ly, the Milky Way would occupy about 15-20 degrees of the night sky in one direction. The concept of Galaxy season would have a completely different meaning.

Thanks. The galaxy has many more stars, of course. Otherwise it would be an open cluster. It's just that they are so faint that they haven't been uniquely identified yet.

Very nice. The problem with this galaxy is that it is so close to Regulus, and risks disappearing in the bright glow. You even got colour in the individual stars. 👍🏽