SharpCap Forums

In the February 2020 issue of Astronomy Now Magazine there was an article entitled Making Light Work. This article contained a section on Wratten Filters and how the various filters could benefit lunar/planetary imaging. Further information to complement this post can be found at https://britastro.org/taxonomy/term/147.

I have some of these filters and loaded up a budget 5 slot manual filter wheel as follows: 1) yellow #12, 2) orange #21, 3) red #25, 4) blue #80A, 5) no filter. This configuration was used on 27th April 2020 against an 18% waxing moon with intermittent cloud. Here is a comparison between no filter (worst image) and a red filter (best image).



Note how the red filter brings out detail on the crater floors and crater walls. The filter has the added benefit of steadying atmospheric turbulence. A filter such as the one used can be found at https://www.365astronomy.com/Castell-25 ... -1.25.html.

Equipment: Celestron C8, JMI Motorised Focuser, f6.3 reducer, manual filter wheel, Altair 183M camera.
Capture: SharpCap 3.2, SER Player (to check test video captures).
Processing: Autostakkert!3, Registax 6.1, GIMP 2.10
Capture Settings: Capture Area = 1920x1200 (reduced area = increased fps), gain = 400, SER 2000 frames,
Exposures: no filter 5.4ms, yellow 4.8ms, orange 6.1ms, red 10ms, blue 8.8ms. These give 60% histogram saturation.

In order to aid comparison, all processing was carried out using identical settings.

AS!3
surface, improve tracking, AP size = 48, stack best 25% (of 2000), output to TIFF.

Registax
wavelet scheme = linear, wavelet filter = default, layer 1 = 10, layer 2 = 30, layer 3 =10.

GIMP
Filters > Enhance > Sharpen (Unsharp Mask), radius = 2, amount = 0.750.
Colors > Shadows-Highlights, shadows = 50, highlights = 50.
Colors > Brightness-Contrast, contrast = 0.010.
Color > Levels, gamma= 1.25

The crop, for comparison, shows craters Endymion, Atlas & Hercules.



All give an improvement over no filter (above) with red giving the best definition. Further testing will be needed as yellow is supposed to enhance lunar mare and blue enhance lava flows and rays. These tests can be carried out as more lunar features become available over the coming days.

The filters will also enhance planetary features and tables describing such can be found on the internet.

Dave

Here is a capture in progress:



Note:

• Use of Target Name

• Exposure, gain, black-level settings

• Histogram saturation at 60%

• Progress at bottom right

• Frame count, no dropped frames, fps at bottom left

Playback of a capture in SER Player to check, note the histogram right-hand-side is around 60%.



Results of processing:



Dave

Wow, thanks Dave. I did not realize that there could be such dramatic differences in sharpness when using a color filter on a camera with the Moon. Thanks for sharing!

Thank you for the study, great work.
Visually, i find light yellow green, number #11 I think it is, gives sharpest view with best detail,
And use an IR pass filter, proplanet 742 for imaging.
As you found, more into the red, steadier the image in average conditions for imaging.

Thanks Andy & Don.

I don't have #11 but have since found a #58 green which I will try. The different colours might have different effects when the moon has greater illumination. I also use an IR685 filter (cost around £50) to good effect, particularly useful during daylight. The cost of just the red #25 is a good investment for anyone who is interested in lunar imaging.

Dave

I was going to make a topic but don't need to.
I am going to use an Baader IR-pass filter for lunar imaging but all new to this. So your topic here is great. For sure some of my setting will be different since it lets through less light but it's a good basis to start with.

Thanks for the comments. The IR pass filter is good for mitigating the lunar brightness. Try this with the IR685 (or whatever you have) - set the gain to around 30% (of maximum possible gain), using a logarithmic histogram adjust exposure so the right side is around 60%. This is a reasonable starting point. My 69% was because the histogram was fluctuating due to intermittent cloud.


Using those guidelines, I managed this with an IR685 filter https://www.astrobin.com/1nsb76/0/.
I did capture Hadley Rille (Apollo 15 landing site).

See viewtopic.php?f=16&t=2473
and viewtopic.php?f=16&t=2475

These are the camera settings:


Exposure was 16ms and gain 10 (out of 29).

If the image looks too dim on the screen it is probably ok (can always be brightened in post processing). If it looks right on the screen it will be over-exposed (burnt out crater rims can't be fixed in post processing).

Good luck.

Dave

Lovely images again Dave.

Here are a couple of mine with C11 and IR filter.

Andy

Really good with great detail on the crater floors/walls and of the rilles. The C11 captures so much more than my C8. What camera do you use?

Dave

Thanks Dave,
I use a Altair Astro GPCAM2 AR0130 mono, and the Proplanet IR 742 filter.