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Everything posted by festoon
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Thanks @vlaiv. So I guess what you are saying is the lens is diffraction limited so having smaller pixels makes no difference. The thing is I saw a massive difference in perceived resolution moving from 6.5um pixels OSC to 3.75um pixels OSC. Obviously less blocky even on widefield targets. Yes this is the Samyang 135mm f/2
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Deep sky imaging in general - I did take some images with this set up of M81 and M82 and as expected the resolution was poor. But I was thinking maybe some of that was down to the fact its an OSC sensor. Also from an inquistive point of view is there a way to calculate what sized OSC pixel size would give equivelent results to a mono setup?
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Currently I'm imaging at 135mm focal length with a an OSC sensor with a pixel size of 3.75 microns. Thus I'm undersampling at 5.73 arcsex/pixel. But I was wondering is my sampling even worse than this because I'm using an OSC with a Bayer Matrix? If so would I see a noticeable improvement in image resolution if I was to use a mono sensor with the same pixel size?
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From the album: Festoon's Samyang 135mm Album
Data from 10/02/21 taken at f/2. 30s subs in total about 90 mins. Equipment AZ-GTi, Samyamg 135mm, ASI224MC-Cool. Processed in DSS, and Startools -
From the album: Festoon's Samyang 135mm Album
Data from 10/02/21 and 30/01/21 taken at f/2. 10s subs in total about 145 mins. Equipment AZ-GTi, Samyamg 135mm, ASI224MC-Cool. Processed in DSS, and Startools -
From the album: Festoon's Samyang 135mm Album
18/02/21 taken at f/2.8. 10s subs in total about 90 mins. Equipment AZ-GTi, Samyamg 135mm, ASI224MC-Cool. Processed in DSS, Startools, Starnet ++, and GIMP -
From the album: Festoon's Samyang 135mm Album
18/02/21 taken at f/2.8. 10s subs in total about 90 mins. Equipment AZ-GTi, Samyamg 135mm, ASI224MC-Cool. Processed in DSS, Startools, and Starnet ++ -
From the album: Festoon's Samyang 135mm Album
18/02/21 taken at f/2.8. 30s subs in total about 120 mins. Equipment AZ-GTi, Samyamg 135mm, ASI224MC-Cool. Processed in DSS and Startools. -
From the album: Festoon's Samyang 135mm Album
18/02/21 taken at f/2.8. 10s subs in total about 90 mins. Equipment AZ-GTi, Samyamg 135mm, ASI224MC-Cool. Processed in DSS, Startools, Starnet ++, and GIMP -
From the album: Festoon's Samyang 135mm Album
18/02/21 taken at f/2.8. 10s subs in total about 90 mins. Equipment AZ-GTi, Samyamg 135mm, ASI224MC-Cool. Processed in DSS, Startools, and Starnet ++ -
From the album: Festoon's Samyang 135mm Album
18/02/21 taken at f/2.8. 10s subs in total about 90 mins. Equipment AZ-GTi, Samyamg 135mm, ASI224MC-Cool. Processed in DSS and Startools. -
Yes I'd agree with this...I think there is more signal to noise in the f/2 image (especially on M42).
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Thanks @carastro. To the best of my ability yes these images were processed the same (using Startools). The results at f/2 (and f/2.8) are pretty amazing. As I was using a colour CMOS I was not using any filters to begin with, and I did notice bloating of the brighter stars but thanks to advice from @vlaiv to use a UV/IR filter the results were massively improved. I was also advised to try f/2.8 hence the comparison here. I don't think the difference is massive at f/2.8 compared to f/2 but I think it can be detected in the images above. Also I'd agree with the comment about how pleasing this lens is - this is a wonderful lens that I am also very pleased with. I've had much more imaging time since I've started using it since its on a lightweight set up that is really easy to carry and set up.
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Here are a few images taken using the Samyang 135mm at f/2 and f/2.8 The sensor used is a ASI224MC-cool with a UV/IR filter. I've tried to keep as many of the parameters the same as possible, including the image processing. One difference to note is the f/2 images were taken on 10/02/21 on a moonless night and the f/2.8 images were taken on 18/02/21 with 38% moon. Going forwards I think I will stick with f/2.8 going forwards, but I'd be really interested to hear what you think. Eitherway, I think its a fabulous lens and give amazing results! The first target is Orion Nebula M42. In each case the subs were 10s long and about 90 mins of data was collected. Based on this image I think the stars are less bloated with the aperture at f/2.8 - especially the brighter stars. There is a little SNR gained by using f/2 over f/2.8 F/2 Image Now f/2.8 image Next target Andromeda galaxy M31. In both cases we have about 2 hours of data. Comparing these two images - they look very similar. Very similar SNR and very similar bloating on stars and star shapes. F/2 image Now f/2.8. The difference in the core of M31 in this image is that I purposely did not tame the core in this image as much as in the f/2, as it did not look natural.
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SGL 2021 Challenge 1 - Satellites
festoon replied to MartinB's topic in SGL Challenges and Competitions
Here is my submission for the theme satellites The title is Starlink, and shows the effect that the SpaceX starlink is having on our sky, astrophotography, and astronomy science. This data was only 1 hour long and taken on 10/02/21. I've processed and merged two images one where the satellite trails where removed from the stack and one where they were not. Imagine how many subs we will have with satellite trails where there are 50,000+ of these in our sky- 25 replies
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Thanks @Paul M. I did see in Sky Safari SES-6 and the nearby USA 170 but thought they were too far away from the actual path to be them. I guess the satellite paths are accurate? I had never thought before that military satellites would not have published data...so this could very well be the mystery object!
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Was looking through my imaging subs the other evening (from 10/02/21 between 23:09 and 23:14 Uk time - location Cambridge, UK) and saw what looked like what I thought was a satellite. The subs are 10 seconds long and animated in this GIF I was intrigued to look on sky safari as what I was looking at - because it took approximately 5 mins to cross my field of view - rather long I thought for a satellite. However, no satellite/object is registered as passing on that date or time. Any ideas/suggestions?
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From the album: Festoon's Samyang 135mm Album
M42 with 2hrs 17 mins of exposure over 2 nights (10/2/21 and 30/01/21) with 10 sec subs. Samyang 135mm f/2 with ASI224MC Cool and AZ-GTi. Stacked in DSS and processed in startools -
From the album: Festoon's Samyang 135mm Album
M31 image taken 10/02/21. 1 hour 15 mins exposure with 30 second subs at gain 60. Samyang 135mm f/2 with ASI224MC Cool on AZ-GTi -
How do I interpret Takahashi diagrams?
festoon replied to JeremyS's topic in Discussions - Scopes / Whole setups
I don't know if this makes a difference, but does not image scale and focal length make a difference when comparing these charts. The DL will be relatively more magnified than the DZ, or are these scales normalised for focal length? -
In my experience it’s a really nice camera. It’s ICX825 sensor is very sensitive and with being cooled there is very little dark current. The only down side compared to a DLSR is the sensor chip size at 11mm diameter. I mainly used this camera paired to a C5 with a f/3.3 focal reducer for EEVA but did save a few of my stacked fits with 5-10 minutes total exposures
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Do you mean Atik 414ex colour? If so yes I do have experience using it. Any specific questions?
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Just a note about the 3.3 reducer...for imaging you only get a limited image circle limited to 1/3" sensors. Any sensors larger than this you get vignetting. If you go down the route of focal reducers for SCTs, a better option may be to go for the Starizona night owl x0.4 reducers for SC. This has a image circle designed up to 16mm.