wimvb

With a dslr on a newt you really do need a coma corrector. You won't get decent stars otherwise. Back focus means that the distance between the back of the cc and the sensor should be 55 mm. Most dslrs have their sensors at 45 mm behind the front flange. Only a few Nikons have a different flange to sensor distance. The t2 camera adapter is 10 mm thick. 45 + 10 = 55, so you're good.

If you have the zwo rgb filters for the as1600, you should be able to use the same exposure time. ZWO have developed these to allow one single rgb exposure time. https://astronomy-imaging-camera.com/product/zwo-new-rgbl-filters-optimised-asi1600 Personally, even without optimised filters, I wouldn't bother with different exposure times. You would also need different darks, because these have to match the lights. With my ASI174MM I use 240 s for rgb and 120 s for L. That works for me. Also, no need to bin the rgb, there is no significant advantage to bin cmos rgb frames, as opposed to ccd.

Great image, well processed. There is a process/script called hdr composition, but I've never used it. https://www.lightvortexastronomy.com/tutorial-producing-an-hdr-image.html

Below the main galaxy is Hickson compact group 56, aka Arp322. Two Arps for the price of one.

A bit puzzled here: the lum master has about the same background median value as each RGB master. With 2.5 times longer exposure time, I would expect the Lum to be stronger. Anyhoo, here's how far I pushed it in PixInsight.

3.5 times the focal length and only 1.4 times the pixel size. Your pixel scale should be 0.49 "/pixel, I believe. (I have 1.2) And you have better guiding rms. If seeing is good, you should be able to pull more out of this.

Thanks, Göran. Yes, it seems so. But I would need a few meter more focal length to see this clearer. Now if only I knew someone who could help .... 😋

Here's an annotated version. I'm not at all certain about the correctness. (Annotated in PixInsight, with added labels from Aladin) Apparently, there are at least two quasars in this image, one (J113447.9+530515) with a reported redshift of 0.53807, and the other (J113459.08+531106.1)with z = 1.258929. But that can't be right, can it?

Thanks, Lee. ngc 3718 has a largest diameter of 5.13 arcminutes. But this size is debatable, because faint arms may reach further than what is given in eg Wikipedia. My camera has a small sensor, and this image has only stacking edges cropped. I cropped a little more than usual, because the data from one night was misaligned. My sensor is 1936 x 1216 pixels

Thanks, Dave. My main sources are Wikipedia and Aladin: https://aladin.u-strasbg.fr/aladin.gml Plus a bit of math (Aladin gives redshift, you still need to calculate distances).

Ngc 3718 is a warped galaxy in the constellation Ursa Major. It is at a distance of approximately 50 Mly from earth. The galaxy has number 214 in Arp's catalogue of peculiar galaxies. Also in this field of view is ngc 3729, which may be interacting with ngc 3718, causing the warped structure in the latter. This interaction has led to the high rate of star formation in the outer arms of the main galaxy, giving them a blue appearance. There is a multitude of galaxies in this image, among others LEDA 2432563, just to the upper left of ngc 3718. This small galaxy has a redshift of 0.178, which puts it at a distance of 2500 Mly. Some of the smaller ones in the area are at a distance of up to 3 500 Mly. The small galaxy group just below ngc 3718 is Hickson compact group 56, aka Arp322. The members of this group all have a similar red shift of 0.0265 - 0.0270, which puts them at about 350 Mly from earth. Some sources quote 400 Mly. That's 7 - 8 times further away than ngc 3718. Acquisition details: telescope: MN190 DS on AZEQ6-GT with ZWO off axis guider camera: ZWO ASI174MM-Cool with ZWO lrgb filters Software: Ekos/Kstars, PHD2 and PixInsight Total integration time: 15 hours (6 hrs Luminance) over about four nights February/March 2020 (click on the image for a larger version)

The advantage of LRGB is that you can control colour and detail separately. The lrgb combination is done at the end of the process. This will allow L to be processed for detail and depth, and RGB for colour balance and saturation.

Excellent result. You have a noisy red background because your camera is picking up the weak Ha signal. You'll need more data to lift it above the noise floor.

What processing software do you use?

That turned out quite nice, Göran. With your 3.5 m Meade, that shouldn't be much of a problem. Hopefully poor seeing doesn't spoil the fun.

Nice! I found this galaxy to be a bit tricky colour wise. But it's definitely worth the effort.

A very nice start already. With 20 hrs of luminance, I think you'll appreciate the background you get with your 1 m fl Newt. Good luck with your project, and CS.

Very nice catch! "Needle in a haystack" comes to mind. 😉

An f/5 seems a safer bet in your case. But the sw 130pds doesn't have much competition.

I think that with any 600 mm fl f/5 system, you will have the same focuser problems you are experiencing already: finding one that fits the tube. I haven't seen any carbon fibre scope smaller than 6" yet. Is f/4 so much harder to collimate? Most scopes keep collimation very well. So once you have them collimated, they pretty much stay that way.

One other test you can do: put the first and last unregistered subs on top of each other and inspect. Is there star drift in the same direction as the streaks in the final image? If so, then it's definitely walking noise. Dithering will help get rid of it.

Alcohol dissolves the oils that protect the skin, and will leave you with dry skin. Use a hand/skin moisturizing product after the alcohol.

Be careful with that. At least on the 150pds, which has a similar focuser, it's possible to tighten the focuser so much that you start bending the spindle.

Yes it does. With any motor focuser, you don't use a focus lock, the motor's stall torque takes care of locking. I found the SW geared dc motor good enough to keep a dslr in place, but it had terrible backlash. The Pegasus focuscube, with its stepper motor, is much better in this respect. It can also hold a camera, efw and oag without any problems. A focuser doesn't need to be the best on the market, it just needs to be good enough for its purpose. Although I have no experience with it, I would probably go with the TS focuser & plate. I think that if it can hold up to 4 kg in place, it's good enough. But check whether you need to drill new holes for the plate. That could become an issue.

I like the variation in colour in image nr 2, but some of the galaxies and stars are too red imo.