GuLinux

Hi,

I was processing yesterday's images in narrowband around the Horsehead Nebula, and I noticed this weird artifact in the stacked image

Initially I thought it was an actual object, with some weird colouring effect due to the palette, but checking other images or star maps didn't show anything for that region of sky.

It's present on all the images for the night (from around 8pm to 4am), with all filters, but predominantly on OIII, so it's definitely not something transient (airplane, satellite, etc). It's also not a spec of dust, as it would show in a fixed position instead after meridian flip rather than moving with the stars:

But it does seem to move around a little bit, given the result on the stacked OIII image:

The shape on a single frame is quite odd as well. It's also fairly small, using the "reflection calculator" tool it would look like a reflection that size would be from something between 1 and 2 mm from the sensor. 

Being this small it's quite easy to edit out, but I'm really puzzled as for what this might be. Any idea?

Thanks,

Marco

Here's another Elephant Trunk.

Data was captured mostly during the challenge start/end dates (precisely 8 Aug 2022 ·  16 Sep 2022 ·  3 Oct 2022), I hope it still qualifies.

Captured in my backyard garden in London (Ealing).

It's also my first picture with my ASI2600MM Pro and Chroma filters.

More info and processing palettes if interested: https://www.astrobin.com/jwti38/

I just got one for my new C11.

I can't really speak from experience, as I only used it once, but can I offer these few points:

• it can't be compared to a dew shield (either homemade or branded), as they serve slightly different purposes. A dew shield will just slow down dew formation, but it will eventually form if the air humidity is high enough, especially if you have a large front lens. The dew heater is an active component, meaning it actually warms up the lens to prevent dew formation (given you provide sufficient power). So the right comparison is between the dew ring and the less fancy dew heater bands you can find for various telescopes. In fact, in the manual, they advise to use the dew heaters in conjunction with a dew shields, as this will allow the heater to operate more efficiently.
• If the choice is between the dew heater bands and the dew ring, keep in mind that the dew ring is especially designed for your celestron SCT, and more efficient. In fact, the main difference is that the dew ring will warm up the lens, as opposed to the regular bands which will only warm up the tube. Eventually, some heat will also warm up the lens, of course, but there'll be heat dispersal, which isn't ideal. The cons for the dew ring are that it's slightly more expensive, not reusable (as it's designed for that specific scope only) and require some assembly (nothing too difficult though).
• Another cons is that the thermistor built in in the ring is only compatible with the celestron smart controller. If you have another controller (DIY, Pegasus, etc) you can still power the ring, but you won't be able to get a precise temperature. I guess you could extrapolate the operating parameters and tune your smart controller, but as thermistors are fairly inexpensive my approach will be to just replace it with another one of known value.

I can join the chorus and confirm I never had any issue with the stability of the plate.

As for the losmandy dovetail, I recently got this from FLO: https://www.firstlightoptics.com/dovetails-saddles-clamps/stellamira-universal-losmandy-style-dovetail-bar.html . I struggled a tiny bit to mount it (there's a couple of washers inside the scope, but they were too narrow for the new bolts) but other than that it's a good fit, and if you want more stability, the design is simple enough to drill extra holes and add a few more bolts (this could be done with the vixen bar as well).

Hello,

I bought this little beastie back in May, but I didn't have enough cloud free time to properly test it - except for a couple of solar observations with my Quark.

Conditions weren't exactly ideal: light pollution, obviously (I live in Ealing, London), then clouds rolled in just when I was ready to start my sequence, shortening capture time by a couple of hours.
Also, the nearly full moon was very close to the target, causing some nasty reflections on the (now cropped out) border of the image.

There seems to be some residual tilt on the camera that I need to fix, and processing could be better, but overall I'm quite satisfied by the result though, the Optolong L-Enhance filter seems to be doing a really great job under such miserable conditions 😂

5 hours of integration time (61x300").

Gear:

• Imaging telescopes or lenses: SkyWatcher Esprit 100 ED f/5.5 APO
• Imaging cameras: ZWO ASI094MC Pro
• Mounts: iOptron CEM40
• Guiding telescopes or lenses: 365Astronomy 50mm Guidescope
• Guiding cameras: ZWO ASI178MM
• Software: GuLinux.net AstroPhoto Plus  ·  Pleyades Astrophoto PixInsight
• Filters: Optolong L-eNhance

Link to AstroBin page

I know it's not the answer you'd like, but registax is, essentially, abandonware.

The last release was on 2011, and a software this old is not really supposed to work on modern operating systems. Plus, there's better alternatives, now.

For my workflow, I use Autostakkert!3 for registering and stacking, and Pixinsight to replace the old Registax "wavelet" processing: I normally use deconvolution (something registax doesn't have), then MultiscaleLinearTransform (which is essentially equivalent to wavelets), then a few more touches here and there (denoise, histogram equalization, etc).

There's probably also free alternatives to pixinsight doing the same things, I haven't investigated so far, but for deconvolution, imppg is a very good choice, for instance.

2 hours ago, Luminated said:

So lucky to get this in London! Wish I had my Skymax already... hoping it arrives before Mars shrinks further...

Ah, yes, telescopes demand is very high lately, and stock is very low in stores..
I was actually thinking of selling my SkyMax, and getting a C9.25 or maybe even a C11, but there would be at least 2 months of waiting, so it's probably better to do it next year, when the major planets are not on "prime time" in the evening

2 hours ago, Luminated said:

Curious to know how this compares to your seeing/visual? What mag where you at?

Hoping for clearer sky’s!

I didn't really have much time to look at it visually, unfortunately  Weather these days changes very rapidly, so I tried to get as many shots as possible before having the clouds rolling in

Mag? You mean visual magnitude limit?

I'm not really sure, to be honest... I think mag 3 or 4 🤔

I live in the suburbs, so it's not *completely* terrible, but definitely not nice either. But at least visual mag doesn't affect planetary imaging

1 minute ago, alex_stars said:

Thanks for sharing the capturing and processing details @GuLinux, as said, makes comparing a lot easier. 😉

Just for reference for those who are into numbers, the sampling scale would be around 0.18 arcsec/pixel. I like to compare that number. In my case I need to barlow for that sampling as my ASI224 MC has a lot larger pixels (3.75 µm in comparison to your 2.4 µm).

Clear Skies.

Yes, I think that my choice of camera and focal ratio really plays to my advantage.

The 178mm is a great camera, the small pixel pitch means I can avoid using a barlow, and still get a good sampling rate (slight oversampling), while the good dynamic range of the camera means I can keep the exposure short and bump the gain without significantly  increasing noise

Thanks everyone

32 minutes ago, alex_stars said:

I agree with @Tommohawk. Its great to see wonderful results of scopes in the 7-8" range as these are more "accessible" to most of us. Not everyone can go and grab a C14. Very well done @GuLinux. Lot's of detail!

@GuLinux, would you share your effective focal length of that photo or the sampling scale. That would be great for further comparisons.

Oh I didn't use any barlow, so native focal length (2700mm), plus a 1.5X resample in software.

I know that on a Mak focal length can vary depending on the focuser position, according to my calculations it looks to be around 2770mm in this specific setup.

Hello, this is my attempt at Mars for this year opposition.

Seeing was "ok" (at least, as ok as it can be in London), but I wish I had a bigger scope to get more details 😕

Telescope: SkyWatcher Skymax 180

Camera: ASI178MM

ZWO RGB filters (left), Astronomik IR Pro Planet (right)

The hole is never needed for optical reasons. It is only needed for mechanical reason, i.e. letting the secondary holder pass through the mask.

Since this is not a problem on a Mak, it's unnecessary to make one

Finally got a decent night for imaging Jupiter and Saturn, very low here in the UK.

Seeing was terrible, but I'm still relatively satisfied with the results, given how difficult these planets are this year from this latitude.

Gear used:

SkyWatcher SkyMax 180 on a CEM40.

ASI178MM, ASI EFW, ASI 31mm RGB filters.

Captured with FireCapture, Stacking with Autostakkert, processing with ImPPG, PixInsight and GIMP.

A perhaps easier way to do the same is to use Stellarium, and a panoramic photo app. On android I found "Google Street View" photospheres to be an excellent solution for this.

There's an article explaining the whole procedure on Sky at Night here: https://www.skyatnightmagazine.com/advice/diy/stellarium-how-to-create-a-customised-landscape/

I normally use Autostakkert, still a windows software, but it works perfectly with Wine.

Registax is far too old nowadays, anyway.

I then postprocess the image using deconvolution on Pixinsight.

I know.. same old easy targets..

But perfect test for my new gear.

I've always been more of an itinerant stargazer, trying to do astrophotography with my star adventurer and camera lenses from dark places, but since the lockdown I've been wondering on how to better use these rare and amazing clear nights.

In particular for this shot I used an iOptron CEM40 mount, with a small 50mm autoguider scope, and a slighly larger (1mm!) Redcat as primary scope.

I also used an Optolong L-Enhance light pollution/narrowband filter, and I wasn't expecting to give such amazing results so close to London Center (Ealing!)

The CEM40 and the L-Enhance are brand new, the Redcat almost a year old, but barely managed to do anything with it, the camera is an ASI094MC Pro.

I also bought an Esprit 100ED and some narrowband filters for my mono camera (ASI183MM), to be tested after I get more confident with smaller scopes

(blog post, FYI: https://blog.gulinux.net/en/blog/2020-06-01-backyard-deep-sky-north-america-and-pelican)

1 hour ago, DaveS said:

That's interesting, but what we need from ZWO are more MONO cameras, OSC is of very limited utility. ATM there's a big gap between the low-end, small sensor and compromised 183 and 1600 and the eye watering 6200 with its huge data sets.

Ditto.

Plus, I'm a bit wary of these full frame sensors. Great on paper, sure, but a lot more difficult to deal with (need for a bigger flat field, more sensitive to misalignments, etc)

Hi @Dantooine and welcome

And as everyone else said, thank you very much for all your precious work!

Aaaand, yes, me too 😂 just spent a massive amount on new mount, apo, narrowband filters (well, we can't look for dark places, so might as well get started in NB) etc etc.

I feel a little less guilty knowing I'm not alone

AstroPhoto Plus.. mainly because I wrote it 😅

I often use KStars/Ekos too for the missing features, usually I use the two of them in tandem

1 hour ago, Zakalwe said:

If it's out of focus then no amount of processing will make it as good as an infocus image.

Yes, of course, I merely meant the illumination issue

6 minutes ago, Zakalwe said:

Make sure that the axis of tilt is along the long axis of the camera sensor. This minimises the distance from the focal plane across the sensor.

Play around with the tilt as well.I have mine set so there is a hint of NRs (which keeps the tilt to a minimum). I usually correct for these faint NRs with a solar flat.

I'll try that, thanks. I often wondered exactly how to find the direction for the tilt, this is indeed a useful suggestion.

I still have to learn how to properly do flats (I've read the "cling film" procedure before, I think I've tried it once, but I wasn't really satisfied by it, but I don't remember why. Have to give it another go)

2 minutes ago, Knight of Clear Skies said:

I found a simple PS tutorial here which may help with the uneven illumination.

Yes, I already followed that one (the second process, subtracting the blurred image). The image I posted is after I already reduced the uneven illumination, it was a lot worse before  😅

Following with interest, as I have the very same problem.

I still have to try flats, but I did buy a tilt adjuster, which definitely helped  with the newton rings, but the camera is now partially out of focus.

It's quite visible in this picture, the centre is quite sharp, while the borders are visibly out of focus, and the illumination is quite uneven.

Nice little Star Adventurer trick I'm testing this evening:

Instead of using sandbags to stabilize my tripod, I bought a few of these: https://www.amazon.co.uk/gp/product/B07RTRHVRB/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Regular pegs might be alright as well, I thought these should offer a better grip, particularly if the cord is well tensioned.

Great review, happy that you joined the club!

And I really hope you're getting better skies than here in the UK, it's been ages since I could last use mine

Quick question.

I'm currently undecided between trying a dual camera setup (with a second camera + lens on the other side of the dovetail, in place or in addition to the counterweight), or to just get a second SA (which would also imply using a second tripod though).

Surely the second might prove to be more stable, but the first setup is tempting, particularly because it would greatly reduce the need for a counterweight.

Did anyone try the first setup? Would you recommend it?