Starwiz

This was my first image with the CLS filter in place. It was captured in the UK six years ago. Orion was low down in the sky and there was an orange street lamp just below where I was imaging, so it shows how good the filter is. John

I'm no expert on this, but logic would tell me that you should be OK if you change the aperture to 3 or above on the lens. This would obviously let a little bit less light in, but you'll be exposing for much longer anyway. John

Yes, perhaps. The noise in the SII channel was very bad for some reason. John

I actually acquired the data for this one back in August, but due to some challenges with the processing, I've only just got round to finishing it. Imaged from Malta. 24.25 hours total integration time in SHO plus an hour of RGB for the stars. John

I've got the Canon 1200d (also astro-modified) and the clip in filter does the job. When I used my DSLR with the CLS filter I was doing up to 15 minute exposures in a Bortle 4.5. It looks like this: https://www.astroshop.eu/broadband-filters/astronomik-filters-clc-canon-eos-clip-filter-aps-c/p,16744 John

The Astronomic CLS filter has a loss of about 8%, so you would need to expose for about 8% longer to collect the same amount of the target light you want to collect. However, the main reason for longer exposures with a light pollution filter is that now you CAN expose for much longer without being swamped by the light pollution. John

A light pollution filter can make a big difference if you're in an area polluted by sodium lighting. Two images from some years back when I was using a modified Canon 1200D. The Orion Nebula, an easy target was without the CLS filter. The Horsehead, a much fainter target, was my first image with the CLS filter and I was amazed what a difference it made. Previously when I'd tried the Horsehead, it was washed out by the light pollution. John

A way to get started with astrophotography is to start by imaging the moon and planets. You can use your DSLR for this when you have a scope to attach it to. Planetary imaging involves taking a video of the object, then using post processing software to stack only the best frames when the atmosphere is at its most stable. This is how I started, using an EQ5 (not motorised at the time), before the bug bit me and I bought an NEQ6. Deep sky astrophotography becomes somewhat more expensive. 🙂 John

Imaged from Malta in SHO over several clear nights during the past couple of months. John

Yes, the 200P.

Hi Stu, For the NB I used Gain=200, Offset=50. For the RGB stars I used 90s exposures with Gain=0, Offset=10. I've since reworked the stars which I think look a little better now. John

Yes, there's still a lot of unwanted artifacts left by Straton to clean up after the stars are removed. It's important to take it slowly to avoid destroying any of the scientific data and it probably took me a few hours on this one.

I'm not totally happy with the stars on this one. I think they could look better but not sure how to improve it further, so any advice is very welcome. Just over 30 hours integration from Mellieħa, Malta over several nights during the new moon period using 15 minute exposures in SHO. The stars were captured separately with a couple of hours of RGB. Stratton was used for star removal from the SHO data. Thanks John

Imaged from Malta over the new moon period. John

Yes, it's common. I have the same with my SW200P. I found light leakage at the focuser and at the primary mirror. I use dark cloth shrouds. The best way to find where it's getting in is to have your camera running in a dark room, then go around with a torch or mobile phone and note where the image changes. John

Can anyone tell me how I go about recording a PEC curve. I can find tutorials on how to use the curve, but not how I get it in the first place. I'm using PHD2 and EQMOD. Thanks John

Thanks, that's great. Here's my contribution: Quasar [VV2006] J140354.6+543246 Magnitude: 20.69 Redshift: 3.258 Lookback distance: 11.8 billion years Indicated by the yellow markers in the image.

I think I've found a quasar in one of my images from last year, that is near M101. I only know this based on a post I saw on CN. What is the best way to validate this if I don't know the name of the quasar? John

A useful explanation for anyone who needs it............. Link: Understanding offset Note: The last histogram is a short video, so you have to click on it to see the results. John

SHO post-processed in Gimp then finished off in PS. John

While doing some more processing this morning, I noticed another artifact, but this one occurs at 90 degrees to the other and is smaller. This also occurs at multiple places throughtout the image. I'm thinking that it might be some sort of alignment feature added by the stacking program, but not cleaned up.

OK, this is rather weird. Ha, OIII and SII stacked in ASTAP. See the two 'stars' at the end of each of the yellow lines. This isn't visible in the individual lights, so I can only think it is some sort of stacking artifact? It appears in all channels. John

It doesn't look that way on my screen. Differences in displays & settings, perhaps.

Yes, I used the 'Average' method and used stars for alignment in both programs, although ASTAP has other alternatives.

Having been a user of DSS for several years, I've recently had a look at the stacking feature in ASTAP. The two images were both stacked using the same lights, darks, flats and dark flats. Ha = 17 x 360s, Temp -10 deg C, Gain 200, Offset 50. 30 x matching darks. 30 x flats 30 x dark flats. The images were stretched to about the same level in Gimp. I then zoomed to 250% and cropped, to show the comparison better. To me, the ASTAP stacked image looks a lot cleaner and a bit sharper too. Has anyone carried out a more extensive comparison between the two stacking programs?