Aramcheck

Before I bought the XT tools I used to largely follow Warren A. Keller's workflow in the "Inside Pixinsight" book. i.e. using Deconvolution to the Luminance (after DBE) followed by MLT for noise reduction & then Histogram Transformation. Once the non-linear Lum & RGB are combined (using LRGBCombination or switching the I in a HSI extract) I used to do a second MLT to effectively sharpen the image & then UnSharpMask. One thing to look into is Pixinsight's HistoryExplorer. You can use it to show all the processes which have been applied to an image & go back to an earlier point in the processing. You can also drag any process which is in the history to the desktop, so if you want to make a change to one process, but want a quick method of re-applying the subsequent steps, you just have to drag the subsequent processes to the desktop, go back to the earlier stage & make your changes & then re-apply the saved processes by dragging them in turn from the desktop back to the image. Hope that makes sense - if not someone no doubt will have demonstrated examples on youtube. (I'd post some screen grabs, but my pc is currently tied up with comet data for the next few days!) Cheers Ivor

I should have pointed out that processing the Luminance separately to the RGB, allows you to control the eventual colours better. In Pixinsight's normalised scale where Black = 0 and White = 1, the apparent colour in any pixel will be lost as the value increases, so to retain the colour towards the galaxy core you want to keep as much of it at values of 0.6 - 0.8, or at least limit the region where the pixels are close to saturation. Applying a gradient mask part-way through stretching the Luminance helps to prevent brightening the core too much, but will then require inverting the mask & applying a softer stretch so that it still appears to get brighter as you get closer to the centre. (It's not something you'd do all the time, but it is an option you can use) It used to be that deconvolution worked best on Luminance only, but in the workflow above I made a mistake applying BlurXterminator only to the Luminance. Watching Russ Croman's youtube interview with Adam Block, it seems that this new tool works best applied to the RGB prior to splitting off the Luminance. Warren A. Keller's book "Inside Pixinsight" is a good primer for the Pixinsight, even though it is now quite out of date. I'd also recommend anything on youtube by Adam Block & if you like his approach to PI/teaching method then his Fasttrack and Fundamentals video tutorials are worth buying:- https://www.adamblockstudios.com/ Cheers Ivor

Hi @Ivor Nice data! I couldn't resist having a quick play. Workflow as follows:- DBE ImageSolver (script) SpectrophotometricColorCalibration BlurXterminator (to Luminance only) (altenatively do deconvolution after extracting Luminance) RGBWorkingSpace (set values to 1) Extract Luminance rename original RGB with the Luminance image I then did:- 3 slight stretches with HistogramTransformation, with the Midtone stretched to 25% StarXterminator (to generate stars only & starless Luminance images) 3 further slight streches to the starless image Applied a small gradient mask to the core of M81 (using Hartmut V. Bornemann's free GAME script); invert & a further slight stretch Invert the mask & apply a CurvesTransformation to brighten the core slightly. On the stars only luminance image, I did four slight streches with HistogramTransformation, with just the Midtone stretched to 25% Used PixelMath to recombine the Luminance stars / starless images using: ~((~starless)*(~stars)) and rename "Lum" Create a clone of the resulting Luminance image, then apply a mask around M81 and apply HDRMultiscaleTransform and then LocalHistogramTransformation. (I create a preview of just the galaxy, make several copies and then try different parameters until I'm happy with the result & then apply those settings to the main image). Then repeat with a mask around M82... finally remove mask and rename "Lum_hdrmt" Use PixelMath to combine the "Lum_hdrmt" and "Lum" images - in this case with 0.5*Lum + 0.5*Lum_hdrmt and rename "L50" On the RGB image I then did:- Repaired HSV Separation (script) ChannelCombination using the output from the above but with the "Unrepaired_V" file & rename "RGB_Repair" Clone "RGB_Repair" and apply MaskedStretch & rename "RGB_MS" (I usually also similarly clone / run ArcsinhStretch and clone / run the EZ SoftStretch script & then use Pixelmath to create a blend... in this case I just chose the MaskedStretch result) On RGB_MS i then ran ChannelExtraction to create HSI components. Delete the "I" image use ChannelCombination with HSI selected, using the H & S images created from the RGB_MS file and the "L50" as the "I" component. Rename the result as "HSI" Extract the luminance from the HSI file and using ScreenTransferFunction / HistogramTransformation create a high contrast image to use as a mask to adjust the colour saturation (rename: Sat_mask) Apply "SatMask" to the HSI image & use Curvestransformation to increase saturation. (Two adjustments were made) Apply SCNR with a small reduction to the Green channel (reduced to 0.9 x original) Apply NoiseXterminator (if using other noise reduction techniques then I would instead do some noise reduction when still linear after deconvolution and then after recombining the stretched images) To reduce the size of Stars I then ran StarExterminator again on a clone & renamed the results "Starless", before running Bill Blanshan's star reduction script... and a final tweak with HistogramTransformation Thanks for sharing the data! Cheers Ivor

From our back garden in light polluted Leeds... SW200pds + ZWO2600MCPRO with IDAS LP3 filter. AZEQ6 mount & OAG guider with ZWO 120MM. I was trying to see if there was any benefit to reducing the sub exposure length from my standard 3 minutes to 60 seconds... NGC1514 - 90 x 60s (16/01/2023) NGC281 - 358 x 60s (16, 18 & 20/01/2023) NGC1333 - 520 x 60s (18, 19 & 20/01/2023) NGC1333 was a hard one to process given our Bortle 8 sky. I used a reference image to try to identify dark regions when doing backgorund removal... Cheers Ivor

When you say you've tested it in daylight, presumably you have already got the scope into focus on a distant object? Assuming that is the case then once polar aligned, and with the focuser at approx. the right distance, I take a short 5-10s exposure in bulb mode & adjust the histogram to show the stars. Then I adjust the focus sligthly & repeat until you've got it reasonably close - as you get closer to focus fainter stars around polaris will become visible & you use the zoom function to finte-tune. Once it's very near focus I then go back to the full view, slew to a bright star and then use the GoTo++ system. I've found that using APT with ASTAP and blind solving is the quickest/most reliable. The GoTo++ will take exposures at whatever settings you have in camera section, so I tend to leave this at 10s. After you've located the bright star, then you can refine the focus further with Bahtinov mask... (I don't use the APT Bahtinov Mask tool - just manually check & if need be reduce the exposure time to 1-2s... Don't forget to remove the mask afterwards though!) I've been using APT since I started about 3 years ago. Since moving to WIndows 11 and replacing the DSLR with a dedicated astrocam (ZWO ASI2600 MCPRO) it's become a bit more unreliable. Cheers Ivor

Images of this 11th Mag. barred spiral galacy in Andromeda don't seem to crop up too often... 13 hr 48min total from our Bortle 8 skies in north Leeds across 4 nights in Dec. (SW 200pds + Baader MK III cc + ZWO 2600MCPRO, with ZWO120mm/OAG guide & IDAS LPS-P3 filter, SW AZ-EQ6 GT Pro mount - 180s subs). I haven't plucked up the courage yet to replace the grease in the mount, which I think is the next step... Also struggling a bit with all the new toys in the Pixinisght toolbox! Cheers Ivor

You will need to look at a short exposure image which is in focus at the centre. If the back focus distance needs increasing then the stars at the edges/corners of the image will be elongated towards the centre & if the stars at the edges are radially elongated then the back focus needs to be decreased. There's a good illustration of this in this old thread:- I had a problem getting decent backfocus with my ZWO 2600 & Baader coma corrector with the M48 connection. As per @alacant's suggestion increasing this from 57.5 to approx 60mm helped:- Cheers Ivor

Welcome to the SGL! Cheers Ivor

I had a go at annotating, but couldn't identify the object - sorry! Solving with Astrometry.net gave Center co-ords as: 16h 33m 26.919s / +66° 12' 01.300" & pixel scale 0.463 arcsec/pixel. Pixinsight's AnnotateImage script then gave the following... Hope someone else can help! Cheers Ivor

Entering the co-ordinates into Simbad comes up with a star ref: TYC 4196-1980-1 -- Star but in Aladin that appears to be the bright star to the right of the unknown object https://simbad.cds.unistra.fr/simbad/sim-coo?Coord=16+32+54.87+%2B65+45+37.4&CooFrame=FK5&CooEpoch=2000&CooEqui=2000&CooDefinedFrames=none&Radius=2&Radius.unit=arcmin&submit=submit+query&CoordList= The object shows up in Aladin, but isn't identified... (DSS2 screen grab from Aladin attached) Curious! Ivor PS: If you can post an uncropped jpeg / resolution details it'll be possible to platesolve & annotate with the PGC galaxy catalogue etc.

I mostly do AP with a SW 200dps on an EQ mount, but recently got a very old 2nd hand SW 200p dob for visual use. Collimation was some way off but it still gave pretty good views. You should be fine with the collimation cap for some time I think. On my imaging 200dps it held it's collimation for about the first year of use. Cheers Ivor

Here's NGC185 a dwarf spheroidal galaxy approx 2 million light years from Earth in the constellation of Cassiopiea. One of at least 13 satellite galaxies which orbit M31. According to the interweb it's total luminosity is about 8 million times that of the Sun and over 70% of the stars are over 12.5 billion years old. Unusually for a dwarf spheroidal, there is an Active Galaxy Nucelus with much more recent star formation in a compact region near the galaxy core. I mainly wanted to have a go at this one to see if any of the galaxies globular clusters could be identified (see annotated close up). Data captured 20/11/2022 from our Bortle 8 skies here in Leeds. SW 200pds + ZWO 2600MC-PRO with a SW OAG & ZWO 120MM for guiding. Only managed 19 x 3 min subs due to cloud & a dewed up secondary (the latter messed up the flat frames somewhat!). Images captured with APT & PHD2. Processed in Pixinsight. Cheers Ivor

Many thanks @coatesg - I'd been wanting to annotate an image of NGC185 to see if I had captured any globular clusters, and this was just the ticket! Cheers Ivor

PI's SubFrameSelector will give you the info for a batch of files, which you can then download to csv. In the Data Unit drop down you can select between measuring the subframes in Electrons / Data numbers or Normalised (0-1). Cheers Ivor

In Stellarium, once you've made the changes have you remembered to click "Save Changes" in the Configuration window? (press F2 to view it) Cheers Ivor

Thanks @Gfamily! Much appreciated Ivor

Hi folks, Does anybody know when narrow band imaging started to become popular in the amateur astro world? (I'm aware of the 1995 Pillars of Creation Hubble / SHO palette) Many thanks Ivor

Thanks @alacant. I had a bit of clear sky this week & had another go with some M48 spacers replacing the Baader varilock (total backfocus now 60.25mm). I wanted to see how the stars changed with camera rotation & with the fan switched off. After calibration I took a few subs of M27 & then rotated the camera, recalibrated & took more subs. My polar alignment was poor (I must have knocked the scope), but I think the results eliminate the camera end of things as the source of the problem. Here's a section from near the middle of the frame:- After M27 I then went to NGC7129 which was at a higher altitude and the source of the elongated stars on the previous session - this time the stars looked rounder but still with the distortion. On the OTA I replaced the SW focuser with a Baader steeltrack at the same time as making the primary mirror cell mod. I'm currently awating delivery of a Hotech SCA laser. Once that arrives I'll check the mirror & focus tube alignment... I'm certain on the IR-Cut filter fitted to the guidecam - it's a cheap Astro Essentials filter. When you say try PPEC do you mean within PHD2, or should I use EQMOD & PecPrep to create / save a PEC curve to the mount firmware? I have to set-up the scope at each session, so I'm not confident that saving a PEC to the firmware would be repeatable. Thanks for pointing out the large DEC movement occuring before the DEC pulse. There may be vibrations when I have to walk past the scope or poor lead management. I use some Suppression pads underneath the scope legs & an old rug to walk on as I have to pass within 1m of the scope when checking the laptop (the flat / dark bit of our back yard is quite small). I should be able to improve the cable management though... I've looked at some of the youtube videos on a dismantle & rebuild of the mount & a pdf guide including this SGL thread. It's definitely something I'll attempt, but only after making sure I've got the mirrors / focus tube aligned as best I can. Thanks again for all your help! Cheers Ivor PHD2_GuideLog_2022-09-29_204409.txt

I usually just let PHD2 select the main star, but with the OAG I've also been adjusting the camera gain. eg if the only visible star in the OAG is saturated then I'll reduce the gain & then re-select it in PHD2. If the chosen star peaks less than 200 then I'll try increasing the gain a bit. Whenever possible I use the multistar. From our back garden guide calibration is a compromise between sky brightness towards the city centre at lower altitude & the available small patch of sky to the south around neighbouring houses / trees. BTW - I've attached a comparison with a stack of the 10s and 180s subs to show the variation in star elongation. I'm now wondering if vibration from the ZWO 2600 fan could be a problem. That'll be easy to check next time... Thanks Ivor

Thanks @michael8554 . I had a go at binning the guidecam x2 last night. Results were as good as x1 but it made it easier to find a star with decent SNR. In the middle of the session I tried switching back to the x1 binning, to see if I could could get a comparison, but the SNR was too low to bother with, so I switched back to the x2. I then had to recalibrate & continue without Dark frames as I messed up 1st time around (cancelling building the dark library after 3.5 secs). Both guide sessions seemed good. I also had to readjust the Baader varilock as it had come loose after the previous session a fortnight or so ago. Star elongation however last night was quite pronounced, but roughly in the same direction in all positons across the image. I tried taking 20 x 10s subs & they look a bit better, but there is still significant elongation. On the 180s subs only about half could be successfully star-aligned in Pixinsight. The PHD2 log measured polar alignment as 0.9' & 0.6'. At the end of the evening I also tried reconnecting the iPolar & that hadn't changed much, so I don't think polar alignment was the cause. The elongation appears I guess about 30 deg from the Dec axis. Early in the evening I also tried taking 20x0.1s subs with Vega de-focused & placed in different parts of the image. Also 1x0.5s sub with vega focused... I'm not sure what if anything these indicate... Have just ordered a Hotech 2" SCA Laser collimator and an M48 to M42 adapter, so I can try next time without the varilock. Hoping also to get some time off work so I can go over the collimation & focus tube alignment. Any advice much appreciated!! Cheers Ivor PHD2_GuideLog_2022-09-24_221843.txt

Ours hasn't been updated in a while...

Found an interesting reply last night on the SGL on the thread linked below from @emyliano2000- I will have to check the alignment of the focuser I think before trying to cut the mirror free. Cheers Ivor

I finally got a couple of spells of clear-ish nights. With the back focus set to 60mm the coma looks much reduced. I've also adjusted the Dec backlash after watching a few youtube videos (Martin's AP, Cuiv The Lazy Geek and Astrobloke). This helped PHD2 to complete the calibration / guide assistant process, although I haven't yet tried binning... On the 12th I thought everything was going ok , but the stars still had a triangular shape. On the 13th I made sure that the primary locking nuts were not touching the mirror cell & took a few shots of Vega whilst varying the focus. (The full sequence can be seen here: https://youtu.be/KuIURZ9u1p8) I also took a set of 10s exposures in addition to my regular 180s ones for a couple of targets - M27 & another near zenith. These also show triangular stars. I didn't bother to dither on either night, to maximise the amount of data I could collect. I presume the next step will be to cut the primary mirror free & to try again with the sealant. Am I missing anything else? Photo of the stacked/unprocessed 10s M27 subs with a STF applied. Thanks again for all the help! Ivor PHD2_GuideLog_2022-09-13_220027.txt PHD2_GuideLog_2022-09-12_213448.txt

Thanks @Clarkey - It looks pretty daunting, but I guess I'll have to attempt it soon. Much appeciated Ivor

Did you follow any particular instructions / video for the AZ-EQ6? Cheers Ivor