Dan_Paris

Imaging galaxies at 49°N around the summer solstice may seem foolish, but here is an attempt during the past week on the Draco trio (NGC 5981, NGC 5982 et NGC 5985), over three nights. Overall 7h20 of luminance data and 80min of color data. Right-click for full resolution: clear skies, Dan Technical details 200/800 custom Newtonian astrograph with Romano Zen optics and carbon fiber tube AP900 CP4 mount on Losmandy HD tripod ASI183mm (0.66"/pix) TS 2.5" Riccardi-Wynne corrector ZWO LRGB filters Guiding : ZWO OAG + ASI120mm mini + AsiairV1 Luminance : 440 *60sec Chrominance : 20*60sec for R and G, 40*60 sec for B Conditions : Bortle 7 skies in Paris' suburbs, rather good seeing (1.86" median FWHM on the luminance stack) Processing with Pixinsight

I think the Maxfield is OK at f/5 but not at f/4 as it adds some spherical aberration. But if you can afford the GPU it is certainly a better option. Is the scope already assembled or is there some possibility of customization, in terms of primary to secondary distance (or equivalently position of the focal plane) and secondary size? Ideally those parameters should be tuned to a specific coma corrector to optimize the illuminated field and the secondary obstruction.

You should tell first which coma corrector you plan to use. Why ? Because the corrector contributes to vignetting as well. At some point increasing the secondary size will not improve field illumination, because vignetting by the corrector takes over. Because the best position of the focal plane (which is correlated to the primary to secondary distance) is dictated by the corrector characteristics (length, backfocus, focus shift).

very nice framing and colors!

Maybe it's time to move from DSS to Siril for preprocessing and stacking, you won't regret it independently of your problem. It gives much better results.

For deep-sky Siril works really well and is simple to use as soon as you understand its logic. Preprocessing and stacking is much faster than with Pixinsight, with nearly identical results. It is my go-to choice for years. For planetary imaging, PlanetarySystemStacker is native Linux: https://github.com/Rolf-Hempel/PlanetarySystemStacker

Well, I thought that the galaxy season was over, but I managed to take another one last week over two nights before the moon was too bright. Certainly the last! Hickson 68 in Canes Venatici is a compact galaxy group about 100 million l.y. away containing the barred spiral NGC 5350 as well as four lenticular galaxies (NGC 5353, NGC 5354, NGC 5355 and NGC 5358), with a bright mag. 6.5 star nearby. The other interesting galaxy in the field is the intermediate spiral NGC 5371, about 130 millions l.y. away. I also like the shape of the small PGC49480 near the top as well as the very distant galaxy cluster below NGC 5371. Right click for full resolution: Clear skies to all, Dan Technical details 200/800 custom Newtonian astrograph with Romano Zen optics and carbon fiber tube AP900 CP4 mount on Losmandy HD tripod ASI183mm (0.66"/pix) TS 2.5" Riccardi-Wynne corrector ZWO LRGB filters Guiding : ZWO OAG + ASI120mm mini + AsiairV1 Luminance : 420 *60sec Chrominance : 30*60sec for each R, G and B filter Conditions : Bortle 7 skies in Paris' suburbs, decent seeing (2.25" median FWHM on the luminance stack) Processing with Pixinsight

Thanks to an unexpected period of good weather this week, I was able to add two new pictures to my galaxies collection. This field in Canes Venatici contains three galaxies belonging to the same group, about 50 millions l.y. away. NGC5033 (top left) is a relatively large spiral with a bright core (active nucleus) but rather faint arms. NGC5005 (top right) is an intermediate spiral and NGC5002 (bottom) is a small Magellanic spiral galaxy. Nights have become very short at my latitude (+49°), about three hours of darkness, so I had to shoot over two nights to get enough data from my light-polluted backyard. There's overall 4h30 of luminance and 25min for each R, G and B filter (right click for full resolution): Then the last two nights I was able to shoot 6h of luminance on M51, that does not need to be introduced, that I mixed with color from last year (right click for full res): Clear skies, Dan Technical details Scope: 200/800 custom Newtonian astrograph with Romano Zen optics and carbon fiber tube on AP900 mount Camera: ASI183mm (0.66"/pix) TS 2.5" Riccardi-Wynne corrector ZWO LRGB filters Guiding : ZWO OAG + ASI120mm mini + AsiairV1 Conditions : Bortle 7 skies in Paris' suburbs, average seeing (2.3" median FWHM on the luminance stack) Processing with Pixinsight

Hi, I was able to shoot only two galactic fields in April due to the bad weather conditions, with my usual setup (200/800 custom Newtonian astrograph with Romano Zen optics and carbon fiber tube, AP900 mount, ASI183mm, TS 2.5" Riccardi-Wynne corrector, ZWO LRGB filters, guiding with ZWO OAG + ASI120mm mini + AsiairV1) First M106 and friends in LRGBH from my backyard (Paris' suburbs, Bortle 7/8) on April 16th (right click for full resolution) Luminance : 320 *60sec, chrominance : 30*60sec for each R, G and B filter, H-alpha : 115*300sec The second picture was shot under much darker skies (Bortle 3) in Southern France (Drôme provencale) but with rather bad seeing. This field contains the beautiful intermediate barred spiral galaxy NGC4725 in Coma Berenices, together with the irregular galaxy NGC4747 or Arp159, the spiral NGC4712 and many others (right click for full resolution): Luminance : 220 *60sec, chrominance : 25*60sec for each R, G and B filter Clear skies to all, Dan

Thanks Alan, it was my first built so it was reassuring to start from something that existed and not from a blank page. I could also test the parts before the project was finished by mixing them with the old ones. In any case, it was a scope that I bought second hand for cheap and I resold the unused parts (mirrors, cell, steel tube etc.) for about the same price. Yes indeed!

Thanks @glafnazur ! It is indeed not very well-known (just 6 images on Astrobin overall), I discovered it only few days before taking this picture.

Hi, here's an image of a lesser known trio of galaxies in Leo, NGC 2964/2968/2970, approximately 80 million light-years from us. There's a long tidal arm emanating from NGC 2968 (the middle one), although I didn't find much info about it. This group would certainly fit in the Arp catalog... The tidal arm was difficult to bring out from the background given my imaging conditions (Bortle 7/8 suburban backyard and hazy sky). However the seeing conditions were rather good (median FWHM 1.85" after stacking). First a crop on the trio (right click for full resolution): Second the full FOV (the framing was chosen to include many PGC galaxies in the background) Thanks for looking and clear skies, Dan Technical details 200/800 custom Newtonian astrograph with Romano Zen optics and carbon fiber tube AP900 CP4 mount on Losmandy HD tripod ASI183mm (0.66"/pix) TS 2.5" Riccardi-Wynne corrector ZWO LRGB filters Guiding : ZWO OAG + ASI120mm mini + AsiairV1 Luminance : 348 *60sec Chrominance : 30*60sec for each R, G and B filter Conditions : Bortle 7/8 skies in Paris' suburbs (20km from the Eiffel tower), good seeing, low transparency Processing with Pixinsight

Thanks a lot Bryan ! I tweaked a bit the processing to enhance the outer parts of the galaxy: What do you think ? Clear skies, Dan

I had rings artifacts with my Newtonian (same size but not exactly the same look), it was coming from reflections inside the coma corrector (whose entry lens was about 10mm above the tube wall). I solved it by adding a baffle at the telescope end of the corrector: an M48 extension tube lined with flocking material (Protostar).

Hi NGC 3198 is a barred spiral in Ursa Major about 47 millions l.y. from us. I imaged it on last Sunday night from my suburban backyard (Bortle 7/8) with hazy sky but good seeing. The median FWHM on the luminance is 1.8". Here is the full FOV, with many small galaxies in the frame (right-click for full-res) : And a crop on the galaxy: clear skies, Dan Technical details 200/800 custom Newtonian astrograph with Romano Zen optics and carbon fiber tube AP900 CP4 mount on Losmandy HD tripod ASI183mm (0.66"/pix) TS 2.5" Riccardi-Wynne corrector ZWO LRGB filters Guiding : ZWO OAG + ASI120mm mini + AsiairV1 Luminance : 345 *60sec Chrominance : 30*60sec for each R, V and B filter Conditions : Bortle 7/8 skies in Paris' suburbs (20km from the Eiffel tower), good seeing, low transparency Processing with Pixinsight

That's really awesome!

Thanks for your message ! Thanks Jody ! clear skies, Dan

Good framing and resolution Olly, a good target for the RASA indeed 👍 Regarding the processing, the end result is a bit too "clean" for my taste. clear skies, Dan

beautiful field and good resolution on these tiny galaxies, well done !

Hi, The Helix Galaxy in Ursa Major, about 42 millions l.y. from us, is one of the few known lenticular galaxy with a polar ring. It is a rather difficult target to image from a suburban backyard, as it is both small and rather faint. Monday night the seeing was vary good (1.8" after stacking) but six hours of luminance was not enough, so I shot six more hours of luminance on Tuesday night. Unfortunately the seeing worsened around midnight. For the final version I retained eleven hours of luminance, with a median FWHM of 2" on the stack and limiting magnitude m=21.2 according to ASTAP. Here's first a slightly cropped version (right-click for full resolution): And a tighter crop on the galaxy: There are many very distant galaxies in the background, including my most distant quasar to date (redshift z=3.827) and a galaxy cluster about 2.7 billion light-years away from us. Thanks for looking and clear skies, Dan Technical details 200/800 custom Newtonian astrograph with Romano Zen optics and carbon fiber tube AP900 CP4 mount on Losmandy HD tripod ASI183mm (0.66"/pix) TS 2.5" Riccardi-Wynne corrector ZWO LRGB filters Guiding : ZWO OAG + ASI120mm mini + AsiairV1 Luminance : 360 *60sec Chrominance : 30*60sec for each R, V and B filter Conditions : Bortle 7/8 skies in Paris' suburbs (20km from the Eiffel tower), variable seeing, low transparency Processing with Pixinsight

Thanks ! Thanks Gorann !I completely agree with you although unfortunately some low-surface brightness galaxies need both transparency and good seeing... (you'll see with my next one 😉) Thanks Martin! The light pollution is rather horrendous but seeing is not that bad. Thanks a lot Justin! Thanks ! The only exception to this general rule, at least for me, is the end of summer when there are some nights with good transparency and seeing conditions. Unfortunately the nights are not yet very long... Clear skies, Dan

Beautiful image of this unusal galaxies with lot of inner details

I like this blend of IFN and galaxies, very aesthetic !

excellent image!

Hi, Monday night the sky was hazy but the seeing conditions were really good. On the stacked luminance the median FWHM is 1.76". The best luminance frames have an median FWHM of 2,1 pix, namely 1.4" or 5µm. I think I never had such results before in broadband. NGC 3184 is a beautiful face-on spiral galaxy in Ursa Major, about 40 millions l.y. from us. It is not very contrasty so difficult to bring out of the sky background, especially in these conditions (Bortle 7/8, haze, quarter moon) so I pushed the integration time to six hours for the luminance. Here's a slightly cropped FOV, with also the little NGC 3179 galaxy and many more in the background (right-click for full resolution): And a tighter crop on the galaxy: Finally the annotated luminance, with many PGC galaxies and quasar labelled by their redshift (up to z=3.33 !). Clear skies, Dan Technical details 200/800 custom Newtonian astrograph with Romano Zen optics and carbon fiber tube AP900 CP4 mount on Losmandy HD tripod ASI183mm (0.66"/pix) TS 2.5" Riccardi-Wynne corrector ZWO LRGB filters Guiding : ZWO OAG + ASI120mm mini + AsiairV1 Luminance : 360 *60sec Chrominance : 30*60sec for each R, V and B filter Conditions : Bortle 7/8 skies in Paris' suburbs (20km from the Eiffel tower), very good seeing (1.76" FWHM), quarter moon, low transparency Processing with Pixinsight