Dan_Paris

Hello, here's the Bubble nebula (NGC 7635) imaged last night with my 8" f/4 newtonian, ASI183mm camera on an AP900 mount near Paris (Bortle 7 sky) and with a gibbous moon. 70*300sec H-alpha for the nebula 30*60sec RGB for stars and color Here's the result with a rather good level of detail (right click for full resolution): Clear skies, Dan

Hello everyone, Thursday night was clear over Paris, albeit humid, with rather good seeing conditions (1.8" FWHM after stacking). For this picture of the famous edge-on galaxy NGC 891 in Andromeda with my 8" f/4 Newtonian, I chose to include in the frame many interesting background galaxies from the cluster Abell 347. First the full field of view (right-click for the full resolution) And a crop on NGC 891 Thanks for looking and clear skies, Dan Technical data 200/800 custom Newtonian astrograph with Romano Zen optics and carbon fiber tube AP900 CP4 mount on Losmandy HD tripod TS 2.5" Riccardi-Wynne corrector ASI183mm ZWO LRGB filters Guiding : ZWO OAG + ASI120mm mini + AsiairV1 Luminance : 240 *60sec Chrominance : 30*60sec each channel Conditions : Bortle 7 skies in Paris' suburbs (20km from the Eiffel tower),rather good seeing but mediocre transparency (high humidity) Processing with Pixinsight

Very clean and detailed, congrats Rodd for this beautiful picture

Lot of details and microcontrast, well done !

Thanks Peter, we should always way for version two before posting ! clear skies, Dan

Incredible image with a huge impact, well done Peter !

Thanks a lot @Elp, @Richard_ and @Paul M, glad that you liked it. Here is a new and perhaps better processing, with more balanced color and better noise reduction. clear skies, Dan

Hi, here is a picture of a fall favorite, M33, from my backyard in Paris' suburbs, over the last days with a 200/800 Newtonian. There is overall nearly 8h of luminance, 5h of H-alpha and 4h of chrominance. Thanks to the small pixels of the camera and the rather good seeing conditions (FWHM is 2" in the luminance stack and 1.75" in the H-alpha stack) the amount of detail is rather nice (right-clic for the full resolution): Thanks for looking and clear skies, Dan Technical data 200/800 custom Newtonian astrograph with Romano Zen optics and carbon fiber tube AP900 CP4 mount on Losmandy HD tripod TS 2.5" Riccardi-Wynne corrector ASI183mm ZWO LRGB filters Guiding : ZWO OAG + ASI120mm mini + AsiairV1 Luminance : 461 *60sec at -10°C, gain 111 H-alpha : 57*300sec at -10°C, gain 111 for each channel Chrominance : 75*60sec at -10°C, gain 111 for each channel Darks, flats and biases Conditions : Bortle 7 skies in Paris' suburbs (20km from the Eiffel tower), rather good seeing. Processing with Pixinsight

Sorry I upgraded to a 2,5 inch corrector and sold the GPU so I cannot send you a picture. For the extension tubes, it is important that their external diameter is 2 inches, otherwise it would not fit in the focuser (and would need to be screwed from inside the OTA, not convenient). Those that I bought on Amazon are I think the sames as those ones: https://www.firstlightoptics.com/adapters/astro-essentials-m48-extension-tube-set-5mm-10mm-15mm-20mm.html Among the set choose the extension that is flush (or protrude just by few millimeters) inside the OTA when it is screwed to the GPU corrector (telescope side), at the correct focus position. The longer it is the more efficient it will be, but if it protrudes to much it would cause undesirable diffraction effects. Then line the inside of the extension with self-adhesive flocking material (in my case, Protostar): https://www.firstlightoptics.com/telescope-flocking-material.html You would have of course to buy more flocking material that needed for the extension tube, but it is in any case a very good idea to flock the inside of the OTA, at least the area facing the focuser, to increase contrast and control stray light.

I see that you use a GPU corrector, with mine I had some issues with internal reflections as well. I found it useful to thread to the corrector (telescope side) a short M48 extension tube linen with flocking material. Of course you need to be careful that it does not protrude, or at least not too much, into the light path.

My personal experience differs from yours. It is true that you need to spend a couple of minutes, not more, to check collimation and tweak if needed each time you set up your gear. Nothing else to fix or tweak. In exchange, you literally save hours compared to a refractor since you collect your data in much less time, to reach a certain SNR ratio. Adding to that that the newt is significantly cheaper than the refractor, in my opinion collimation does not weigh a lot in the balance. Of course I compare a common Newtonian astrograph (say 200/800) to a typical refractor of similar focal length (say 120/900). Regarding spikes it is a question of taste, so a newt is indeed a poor choice for someone that does not like them (some solutions exist though).

I have a soft dew shield on my Newtonian, that I remove for taking flats (with a flat panel). Never seen anything suspicious on calibrated subs. Note that I fasten the Velcro at some angle, such that the dew shield is slightly conical, in order to be sure that it does not cause vignetting by itself.

This is precisely the issue with this corrector, it introduces a hint of spherical aberration at f/4 (I tried it) but at f/5 it should be fine. The GPU is good but more expensive, and its length could be an issue if the focal plane is not far enough (which is likely the case for a 150/750).

You're right, its an important point. This one is good for an f/5 scope and not very expensive : https://www.firstlightoptics.com/coma-correctors/ts-95x-maxfield-coma-corrector.html

If you're looking for big and fast, a 150/750 Newtonian is a perfect match for an HEQ5 mount. Its focal length (more than twice that you have) would open the door for many objects that are too small for your current refractor, in particular galaxies, while keeping integration times reasonable with its low f/ratio. Even the most expensive models, like this one: https://www.teleskop-express.de/shop/product_info.php/info/p13462_TS-Optics-6--f-5-UNC-Newtonian-Telescope---Carbon-Tube---made-in-Germany.html are significantly cheaper than the 90mm APOs that you suggested.

Hi, NGC 7640 is a nearly edge-on barred spiral galaxy in Andromeda, with a relalatively large angular size but low surface brightness. Last week I shot nearly 4 hours of luminance and 1h30 of chrominance with my 8" f/4 newtonian astrograph, from my garden in Paris' suburbs (Bortle 7/8). Here is a crop on the galaxy And the full FOV As this field is close to the galactic plane, there aren't much galaxies in the background. Thanks for looking and clear skies, Dan Technical data 200/800 custom Newtonian astrograph with Romano Zen optics and carbon fiber tube AP900 CP4 mount on Losmandy HD tripod TS 2.5" Riccardi-Wynne corrector ASI183mm ZWO LRGB filters Guiding : ZWO OAG + ASI120mm mini + AsiairV1 Luminance : 230 *60sec at -10°C, gain 111 Chrominance : 30*60sec at -10°C, gain 111 for each channel Darks, flats and synthetic biases Conditions : Bortle 7/8 skies in Paris' suburbs (20km from the Eiffel tower), average seeing (2.4" after stacking) and transparency Preprocessing and stacking with Siril, processing with Pixinsight and Rawtherapee

Congrats for having captured the ring, not an easy task!

Very smooth image yet with very fine details, well done Rodd!

What's nice from ZWO is that most features of the firmware updates, even the most recent ones, are implemented on the v1 (one exception, for instance, being plan mode). And of course bug corrections. I still use it and, although plan mode would be nice to have, I don't really feel a need to change it. It does everything it needs to do, including polar align, AF, and multi-star guiding.

I use this camera with an OAG on my 8" Newtonian, but its focal length is shorter (750mm). As in your case I never had an issue to find guide stars (using 3sec guide exposures), usually the multi-star algorithm picks 5 to 10 stars. Btw it may not be useful at all to have a rather bright star as a guide star. To avoid saturation you would need to lower the gain and/or the exposure but in that case the multi-star algorithm may not work.

Awesome image with a stunning 3d effect and perfect framing ! This is indeed a nice target with longer focal lengths, I had visited it two weeks ago I didn't realize that its surroundings where that dusty...

That's a very good picture with a clean and detailed look, well done !

Thanks Martin ! Dan

Thanks a lot @MartinB, @ncjunk and @mackiedlm for your kind words ! Dan

Thanks a lot Steve ! I had concerns about the outcome 😂