David's Astronomy - Notes 2023-01-18 (S1088)

Initial images acquired during the initial stage session were noted to have poor resolution (Jupiter) or have very uneven illumination (see pictures of below) . A visit out to the observatory show that the entire interior surface of the LX200's front corrector lens was covered with condensation (this was interior / no exterior condensation or dew). The problem is also certainly due to water entering the LX200 tube following an incident in the last session when snow slid down onto the front of the telescope (see Snow slid off shutter onto scope, 2023-01-16). Although the snow /ice was removed the following morning, some evidently melted (due to dew heaters and later due to hairdryer) and entered the interior through small gaps in the outer ring.

Whilst stars were visible through the telescope/camera system and images were ok for initial focusing, for taking locate frames for centering and later on for guiding, the quality of the main images taken were too far compromised to be useful and were later all rejected. With no quick resolution to the problem the observing plan for the rest of the night was abandoned. However in order to still get something out of the observing session whilst skies were still clear, operations were switched over to using the TS80 Secondary Scope for imaging with the LX200 used in support for centering & guiding.

When checked the following day the condensation on the inside of the corrector lens had reduced to a dougnut around the secondary mirror but condensation was seen to be present over the entire surface of the primary mirror (this may have been present earlier during the session) or it was condensation of water vapour being driven off the corrector lens by dew heaters).

The SBIG Camera was removed from back off LX200 and warm air blown into the interior of the scope. This was interspered with an attempt to suck humid air out of the tube using a portable vacum cleaner. A backup dew heater band was placed around the telescope tube at the position of the primary mirror and the heater power turned up to 100% for both front and rear dew heater bands. A hair dryer was used to 'shift' the doughnut of condensation around the secondary mirror. The condensation on the primary mirror had mostly cleared.

Three hours later and the doughnut of condensation had reformed around the secondary mirror but the primary was more or less still clear. Hiar dryer was again used to 'shift' the doughnut of condensation on the corrector lens (inside surface). A muslin bag of renewed-dessicator had been prepared and was placed in the rear opening of the scope. This will be left in place for 48 hours in the hope that residual humid air can be dried out.

No sign of any internal condensation 2023-01-21 17:00. SBIG Camera reattached in preparation for night time setup to ensure measured camera alignment is at 180

Raw Image showing anomalous illumumination / background		Raw Image showing anomalous illumunination / background


Photo showing snow /ice on front of telescope optics caused by snow sliding off shutter onto front of telescope at end of previous session (2023-01-17)		Photo showing condensation still present inside telescope at end of session (2023-01-19)

Corrector Lens found to be clear of condensation 20 hours after putting bag of desicator into back of scope. Some light condensation on primary mirror. Some extra warm air blown into interior and then dessicator bag put back. SBIG Camera reattached to back of telescope on 2023-01-21.
Camera Rotation and Telescope Point had to then be adjusted in the following live session.

Update 2023-02-01

The S1094 Session on 2023-01-29 and the previous two or three sessions (S1093 - S1091) showed relatively poor transparency (low normalised ZP values) that seems to deteriorate through the session. Although the loss of transparency doesn't effect the imaging of stars (at least not to a noticeable level), the effect on galaxies and other faint objects is much more noticeable.

Daylight investigation on 2023-02-01 shows condensation on the primary mirror, which is a probable ongoing consequence of the incident in session S1088 when snow slid off shutter onto front of LX200 onto front of telescope (notes). Although an attempt was made to dry out the interior of the LX200 telescope tube after the S1089 session (see notes above) it is presumed that the sufficient humidity remained that condensation was still able to form on the primary mirror when it is pointing towards the cold sky, loosing temperature in the process.

A new attempt was made to dry out the interior of the scope on 2023-02-01, using a 12" dew band at the position of the primary mirror, a hairdryer blowing hot air into the telescope tube via the visual back alternating with vacuum cleaner with extension inserted into visual back extracting air from the telescope tube. Camera to be reattached ahead of next session (S1095) and its rotation and pointing to be adjusted at start of the next session.

Update 2023-02-09

Problem with condensation inside LX200 finally resolved through the purchase and use of a Lymax SCT Cooler (See Notes - Lymax SCT Cooler, 2023-02-09).

Latest Siril version, 1.0.6 (dated 2022-10-18) was downloaded from the siril.org website (https://siril.org/) and installed on the Development Computer today (2023-01-22). The intention is to follow up on initial look at Siril 0.99.6 (1.0.0 beta) in Nov 2020 (see earlier notes), and see how the current version of Siril can be utlised for processing OSC images taken with ZWO 178MC camera.

Opening a ZWO ASI 178MC OSC image captured using a SharpCap

Set CWD (Current Working Directory) to
C:\Data\ZWO Imaging\SharpCap\2023-01-18 S01088
and later to
C:\Data\ZWO Imaging\SharpCap\2023-01-18 S01088\M42\01_14_25
Opened ..\M42\01_14_25\M42_00001.fits (12.2 MB) with Debayer checkbox ticked
Colours in RGB picture wrong

Went to "Fits/SER debayer" tab in Preferences
- set "Bayer/mosaic pattern:" to RGGB
- unticked the 'Bayer information from file's header if available' checkbox. (colours incorrect if this was left ticked)
- kept "Debayer interpolation:" as RCD (SiriL's recommened method)

Reopened M42_00001.fits
Colours in RGB picture now correct.
Looked at image in Linear & in AutoStretch Display Modes
Downloaded the script OSC_Preprocessing_WithoutDBF.ssf: (pre-process color images without dark, bias nor flat)

(from https://free-astro.org/index.php?title=Siril:scripts site)

############################################ # Script for Siril 1.0 # August 2020 # (C) Cyril Richard / Colmic # OSC_Preprocessing_WithoutDBF v1.0 # ########### PREPROCESSING SCRIPT ########### # Script for color camera preprocessing # needs 1 set of RAW images in the working # directory, within 1 directory: # lights # ############################################ requires 0.99.4 #preprocess lights cd lights convert light -out=../process cd ../process preprocess light -debayer #align lights register pp_light #stack calibrated lights stack r_pp_light rej 3 3 -norm=addscale -output_norm -out=../result cd .. close

Moved raw M42 fits files into 'C:\Data\ZWO Imaging\SharpCap\2023-01-18 S01088\M42\01_14_25_Siril\lights'
and changed SiriL's working directory to 'C:\Data\ZWO Imaging\SharpCap\2023-01-18 S01088\M42\01_14_25_Siril'
Executed the "OSC_Preprocessing_WithoutDBF" script using command "@ OSC_Preprocessing_WithoutDBF.ssf"
which ran and created the stacked file "result.fit " (73.6 MB).

Opened result.fit & displayed image with Auto-Stretch display mode.

Saved image as a .png file (SiriL gave the message "Viewer mode is not linear", clicked the Save Anyway which produced a Linear scaled .png file, 26.8 MB). Image below (resized to 16% size)

With the image displayed to fit window, using "Take Snapshot of displayed image" options 'Save as unique file' and 'Copy to Clipboard' save the Auto-Streched image at the displayed size (0.3 MB). Image below (resized to 16% size equivalent)

With the image shown at its normal size, the 'Take Snapshot of displayed image" options produce a file or clipboard image that is cropped to that portion of the original image that is currently visible.

Subsequently, the ASINH image processing function (available through GUI) was used
Copy 'OSC_Preprocessing_WithoutDBF.ssf' to 'OSC_Stack_Test.ssf'
and added a command line near the start

cd 'C:\Data\ZWO Imaging\SharpCap\2023-01-18 S01088\M42\01_14_25_Siril'
Opened Cmd

$ cd C:\Data\SiriL\scripts
$ 'C:\Program Files\SiriL\bin\sirel-cli.exe' -s OSC_Stack_Test.ssf >t.log
Useful commands

load filename
asinh 30
savepng filename2
$ siril-cli.exe -s script_file
Information on siril-cli.exe at https://siril.org/docs/man/
Data Sizes
- Single Raw File from SharpCap (1x1, 16 bit, ZWO 178MC) = 12.2 MB
- Folder (lights) with set of 20 images (16 bit OSC) from SharpCap = 245 MB
- Folder (process) generated by Siril processing of set of 20 images from lights Folder = 3.11 GB
- Final Stacked File from Siril (1x1, 32 bit) = 73.6 MB
Targets from S1088 processed using Siril were:
C/2022 E3 (ZTF), B33 (IC 434), M35, M37, M38, M42, M45(part), M67, M95, NGC 2158 (see Images S1088, 2023-01-18)


	Session Aims & Highlights
	- Observing Result - Night Summary Plot - Session Event Log

	Operational Issues
	- Critical Issues (0), Major Issues (2), Minor Issues (12) Small Defects (5), Continuous Improvement (7)

	Images from 2023-01-18 >>

	LX200 - Condensation inside Scope

	Siril (1.0.6)

This Web Page:	Notes - Session 1088 (2023-01-18)
Last Updated :	2024-09-25
Site Owner :	David Richards
Home Page :	David's Astronomy Web Site

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Notes - Session 1088 (2023-01-18)

Session Aims & Highlights (2023-01-18)

Operational Issues (2023-01-18, S1088)

LX200 - Condensation inside Scope

Siril (1.0.6)