Hughsie

2 hours ago, Elp said:

Think you've got other problems...

They should have called me for the new Andrex advert.

Morning Rob. Having run the image through nova.astrometry.net the image scale comes in at 0.589”/pixel. With the sensor pixel size at 4.63um this equates to a f/l of 1621 mm whereas the advertised f/l is 1600 mm. Having read numerous user reports on RC’s this is not uncommon for these scopes and if I was going to sweat on this I would be looking for a Ronchi eyepiece to verify if this is correct, too short or too long a f/l. But I’m not going to tinker down this rocky road 🙂

As to the focal ratio, I read somewhere that the Primary Mirror on an RC is somewhere in the f2 to f3 range and the secondary has a magnification of 2.5x to 3.5x. May be the difference is down to the specs of the mirrors.

But the main issue here is you only live 5 mins from me and it should have been you on the ground with the Allen keys and me watching the laptop screen!

On 11/04/2024 at 20:09, Mark_C said:

Very nice!

Regarding flats, I also do the same, I use an A4 ring binder wallet that I've separated in to one single sheet then wrap it around the OTA dew shield with an elastic band. I then higher the exposure so that it's at around 60% in the histogram, then get SharpCap to take the flats, seems to work just fine and the results seem to be decent. I think this is the way DayStar advise to take solar flats, or use one of their dedicated flat screens (that do pretty much the same thing but more convenient.)

I use a crumpled up sandwich bag over the front of the scope held on with a lacky band. Beats paying what DayStar charge for their flat panel!

When I store my data for the future after using WBPP I generate the following folders;

• The original data from across one or more nights excluding flats, dark flats and darks.
• A folder called Final Images in which I keep an XISF and JPEG version of the final processed image and any annotated images.
• Lastly a folder called Master Lights & Calibration Frames in which I keep the post calibrated and integrated light frames pre-processing plus the Master Flat and Master Dark generated by WBPP.

Although I have a darks library which I update once a year, I keep the original master dark used in calibration for the current imaging session in case the camera sensor changes over time. Like Ouroboros, I will only delete the individual flats and dark flats subs once I am satisfied the Master Flat has calibrated the lights properly.

2 hours ago, Rallemikken said:

Very nice picture. I'm considering one of those for next season, most likely the StellaLyra 8" f/8. What camera did you use on this?

I used the ZWO ASI294MC camera with a UV/IR cut luminance filter. The camera sensor has a 4.63um pixel size which leads to a slight over-sampling. I have also used the ZWO ASI1600mm which has a smaller pixel size. When using this I will still use bin 1x1 and then resample the image to 2x2 when processing the data to see if there is an improvement or not.

The scope I used is the same one you are looking to purchase. Don’t be put off, the poor collimation was all my doing and a lack of understanding on my part on the mirror dynamics. Collimating these can be a challenge but it just requires a methodical approach and a star test. Worth researching online to see what method may best suit you. Having said that, once collimated they hold very well and probably need checking once a year.

The final thing I would add for you to consider is the stock focuser that comes with it. In summary it’s pants. Build into your budget the cost of a new focuser, the Baader Diamond Steeltrack is available through FLO along with the adapter to attach it to the RC8. I bought this and it’s a marked improvement. You pays your money and takes your choice when it comes to accessories but I would hold fire on things like flatteners, reducers and tilt adapters. This image was a bare bones camera/filter/native 1600mm image with the Baader DST. 
 

I hope this helps.

John

12 minutes ago, Vic L S said:

I actually use PixInsight, and WBPP to integrate my files, I should have mentioned that in my post. 

When doing multi-night projects I save all my data by night. In each folder will be the lights, flats and dark flats captured for that session. If the project has the same camera settings such as exposure time, gain and temp then there will only be a single master dark otherwise there will be different darks to reflect those camera settings as well.

In WBPP you can view a calibration diagram for each set of lights to ensure the correct flats and darks are being used. It helps to be methodical otherwise it can become confusing. If WBPP selects the wrong calibration files then you can override it. 

Another setting to be aware of is the exposure tolerance. This defaults to 2 seconds. WBPP will integrate all calibrated lights with the same exposure time but you may have used different exposure times during the project and still want the data integrated into a single master light. For instance, one night you may have collected subs at 300 s exposure and a second night at 180 s exposure. By default WBPP will produce two master lights one representing 300 s data and the other for 180 s. There may be good reason why you want this eg where you want data not blowing out cores on globular clusters. If you don’t need them to be separate then you can adjust the exposure tolerance from 2 to 120 s (300-180) and WBPP will combine the lights data post calibration for you.

Hope that helps.

John

26 minutes ago, RobertI said:

That looks excellent John, I think you might have finally nailed the collimation. 

Thank you Rob. Just have to check the secondary one last time then, fingers crossed, we get some clear nights.

I own an RC8 which has been a source of frustration for over 4 years. When I first bought the scope I tinkered with the collimation. What was I meant to do when a regular feature in the forum topics is the heading 'Ritchey-Chretien Collimation....', I thought everyone enjoyed collimating them. How wrong could I be.

So I tinkered so the collimation got bad, then tinkered some more until it was horrendous and finally when I thought I could tinker no more.....I tinkered again!

The RC8 was like a loveless marriage but we both needed each other. The RC8 needed me to be able to see again and I needed the RC8 for the challenge of getting the poor thing fixed. So, last week I stripped it down to its bare bones (no I didn't remove either mirror, I am not that stupid) and started again. Having gone backwards and forwards between aligning the primary mirror with the optical axis then adjusting the secondary and back again I reached the point where I was only making the tiniest of adjustments. Time for a star test!

Now, there is nothing I enjoy better than a dark night with two tiny Allen keys, a scope pointing at the Zenith, me laying under it figuring out which part of my varifocal lens glasses gives me the best focus and finding that I have just crushed two amorous snails. Seeing wasn't great and common sense said that I should wait for a better night but they are few and far between in the UK. I restricted myself to a loosening tweak here and a tightening tweak there. 

The out of focus star looked......good? Never a word I have used with the RC8. Anyway, I slew the scope to M51 as it was due to cross the Meridian to the South and rattled off 17 subs at 2 minutes each. I actually captured more calibration frames than lights so to be honest but I wasn't expecting much other than good looking flats.

Here is the result. As I say, it's just 34 minutes integration time and I was very surprised. Still, just a few more tweaks here and there and ..........

Just adding my input;

Anything generated by BBC weather I ignore.

Metcheck has been fairly reliable for me and has an astronomy forecast.

Windy is a also a good free programme. I select clouds at all heights and you can run through the night hours to see it’s prediction as to what cloud may roll in.

In any event, I never rely on a single source - first I check Metcheck, then see how Windy I am, decide if my all-weather knee feels like rain is on its way then use my Mk I eyeballs.

1 hour ago, Dave Smith said:

I wa out earlier but did not see that eruption. Well done.

Dave

Hello Dave,

I didn’t see it on Gong Ha before I started and I even went looking around the limb to observe what was there but didn’t see it either. It was only when I started processing the disc after the session  that it’s presence revealed itself.

The tilt adapter would sit between the camera and diagonal. Typically the camera screws into one side of the tilt adapter and a 1.25” nose piece would screw into the other. The nose piece is then inserted into the diagonal. 

You have two potential issues. 1) the asi120 is prone to newton rings. Even with a tilt adapter there are comments on other forums where even the maximum tilt in the adapter wasn’t enough to remove them. 2) I haven’t seen a tilt adapter that fits a mini version of the asi cameras. That’s not to say there isn’t one, I just haven’t seen one.

Like Elp, I am of the opinion that flats will not calibrate out Newton Rings this is because they appear in the flats too. To capture flats I would point the Lunt towards the centre of the Sun, remain in focus and put an opaque plastic bag over the front of the scope secured by an elastic band. Something like a crumpled sandwich or freezer bag works but it needs to be clear/whiteish. Pull the bag tight. Then adjust your exposure time so that the histogram peaks around the 50% mark and capture your frames, say 100 in SER format.

In Autostakkert you can create a master flat and open the SER file. Autostakkert will then stack and produce a master flat in tiff format which you can then load into Autostakkert to calibrate your images.

Hope that helps.

John

1 hour ago, Vinnyvent84 said:

John, thank you so very much. This is extremely helpful. I have ALOT to learn and my gear gets here on Monday. I have a ASI533MC and am pairing it with a Redcat 71 WIFD ASIair Plus and AM5. Your information most definitely helps. 
 

Im currently trying to research how long my sub exposures need to be considering I’m in a Bortle 8 and using OSC. This, along with many other things - but you now scratched one concern off my list so thank you again!  

A great resource for research is Astrobin. If you haven’t heard of it it's a community of photographers who post their images/have forum discussions. It is free to join. You can search by location, say New York, and view images posted by individuals near you. In the main they will list the equipment used and exposure times. You can also search by equipment such as your camera and view images and see what camera settings have been used.
 

It’s a great way to see first hand what combination of equipment/exposure times will produce and to look for potential targets. Worth a look if you haven’t already.

1 hour ago, Hughsie said:

 

I get the following error in PixInsight using MacOS (Intel) platform. I have reset all the repositories and updated them again but still get this error for GraXpert and GraXpertDenoise.

 

Processing script file: /Applications/PixInsight/src/scripts/Toolbox/Graxpert.js

*** Error: Signature verification failed for 'GraXpert': Invalid code signature: /Applications/PixInsight/src/scripts/Toolbox/Graxpert.js

Resolved. Updated to build 1605.

I get the following error in PixInsight using MacOS (Intel) platform. I have reset all the repositories and updated them again but still get this error for GraXpert and GraXpertDenoise.

Processing script file: /Applications/PixInsight/src/scripts/Toolbox/Graxpert.js

*** Error: Signature verification failed for 'GraXpert': Invalid code signature: /Applications/PixInsight/src/scripts/Toolbox/Graxpert.js

Hi Vinny.

You are correct regarding darks. These can be captured in advance and are not affected by changes to the image train. What you do need to remember is that your darks need to be captured using the same exposure time, Gain, Offset and Temperature as your light frames. I have a 'Dark' Library for my ASI1600mm and ASI294mc all at a temperature of -10c. For each camera I have exposure times for 60s, 120s, 180s and 300s. The Gain and Offsets for the 1600mm are based on whether I am doing narrowband or broadband imaging. For the 294mc I tend to use a Gain of 121 and offset of 30. I refresh mine every 12 months.

It's best practice to take flats after every session to ensure the best calibration outcome. You can use flats from previous sessions only if your image train has not changed and assuming you keep your optics free from dust. As you mention, changing the image train between capturing your lights and taking your flats will result in poor calibration so don't touch anything. 

In regard to the filter wheel, as you take your flats for each filter the wheel will rotate round and your filters will be in the same orientation as they were when you captured your light frames so this doesn't impact the image train. The only way this will not be the case is if you alter your image train by moving the filter wheel or unscrew the filters and put them back in again. As to the rotation of the wheel moving dust, you would have to be pretty unlucky for this to happen, however, it does no harm to periodically inspect your optics to ensure no dust or other particles have snuck their way in.

Hope this helps.

John

Full details and RGB version can be found on Asstrobin https://www.astrobin.com/users/hughsie/collections/2342/

Solar disc.

Lots of Active Regions.

AR13639

AR13639

AR13643

AR13644

Prominences on the southern limb

Prominences on the south east limb

Abell 1656 - Coma Galaxy Cluster and Quasar Hunt

With all the poor weather in the UK so far I had a rare clear night on 9th April 2024 and a New Moon as well. Here is Abell 1656 in Coma Berenices. There are some 100 quasars (green label), a planetary nebula (red label) and too many PGC galaxies to count in this image. Nice to see that I managed to capture some bright pixels for the Quasars as well.

Equipment & Data

William Optics Z103 refractor.

ZWO ASI294mc Pro with Chroma Lum filter.

Sky-Watcher EQR6-Pro mount.

161 x 120" subs, Gain 121, Offset 30, Sensor temp -10 c, Bin 1x1

24 minutes ago, Paul M said:

As I often do with other's images, I took the liberty of downloading, solving and investigating this fine image, just to see what's there.

I expected there to be a few Quasars in there, so using ASTAP annotation filtered for QSO's, I got the result below. Rather a lot of them! 🤪 and it looks like you got a few pixels for many/most.

 

Thank you Paul. I ran the same in PixInsight using the TypeCat script and pulled out a lot of quasars. Currently, calculating the distances on a few to see if I’ve beaten my most distant object captured.

With galaxy season upon us and the weather in the UK being so poor I had a rare clear night during a New Moon on 9th April 2024. With more poor weather being forecast I decided to get my 'galaxy fix' by photographing Abell 1656. This region of space contains over 1,000 identified galaxies so that ought to scratch that galaxy itch!

Equipment

• William Optics Z103 refractor.
• Main camera - ZWO ASI294MC Pro; Guide Camera ZWO ASI290mm mini.
• Chroma Luminance filter.
• Sky-Watcher EQ6-R Pro mount.
• Primaluce Lab Sesto Senso motor focuser.
• Pegasus Astro Ultimate Powerbox V2.
• Pegasus Astro FlatMaster 150.

Software

• N.I.N.A.
• PHD2
• PixInsight.

Data

• Chroma Lum 161 x 120" (Gain 121, Temp. -10c, Bin 1x1)
• Darks 50
• Flats 30
• Dark Flats 30

AR13639 (Class EAI)

Located N30E12, this region contains 16 sunspots and has reduced in size over the last 24 hours to approx. 880 million square kilometres. It released no flares today, however, it did produce an M4.02 class flare on 15th April 2024.

AR13644 (Class DSO)
Positioned just off the eastern limb at N13E49, this small region is made up of two sunspots and has increased in size to 364 million square kilometres. It has not produced any flares to date.

AR13646 (Class CRO)
Finally, we have a small grouping of eight sunspots just north of AR13644 at N22E47. Like AR13644, this region has increased in size in the last 24 hours to some 210 million square kilometres. At this time it has not produced any flares.

Equipment

• William Optics Z61 refractor.
• Tilt adapter.
• ZWO ASI174mm camera.
• Sky-Watcher EQ6R Pro mount.
• DayStar Quark Chromosphere.

Data

• 110 images from 1,000 stacked.
• Exposure time 18ms, Gain 0.

Software

• SharpCap Pro.
• Autostakkert4!
• PixInsight Solar Tool Box.

I originally captured the data from this image in Sii, Ha and Oiii across three nights in 2021 using scope T14 at iTelescope.

The data was automatically calibrated and downloaded from iTelescope but other than initial stacking I never posted the image as the camera had line defects. Whilst PixInsight did its best to remove most of the lines there were some persistent offenders and so I binned the project.

Today, with a bit more time on my hands I decided to have another go and feel I have something presentable to share this time around. There remain some red and green blotches from the camera which you can see zoomed up close but as Mother used to say, "A blind man would be pleased to see them".

Here is the Seagull.

5 hours ago, RobertI said:

This looks great, lots of detail in the core now. More detail all round too. Great job. 👍

Cheers Rob. 2022 must have been my "blurry period" lol

6 hours ago, PatrickO said:

I have no skill in DSO, but these are beautiful images. Well done.

Thank you Patrick, I appreciate your comment. I just muck around with the data, throw it together and keep going backwards and forwards until I get where I want to be.