Equipment for the Transit of Mercury

[michael8554]

I've been gearing up for the Transit of Mercury on May 9th.
I've made a 60mm sub-aperture Baader filter for my 200mm F/6.3 SCT.
I've made some test stills and avi's with a mono-chipped Toucam Pro (Atik 2HS).

I'm disappointed with the sharpness, should I try a full aperture mask?

I should mention that I was very pleased with the avi's I took of the Transit of Venus in 2004, but that was with a 125mm F/15 ETX and colour Toucam.

Michael

[cathalferris]

Is the Baader filter material stretched, or is it slack across the window?

It's supposed to be slightly wavey and loose, and not taut at all. Stretching the filter material can cause problems with the view.

[michael8554]

Thanks Cathal

Not particularly tight, but I'll experiment and see if it improves.

Also thinking that I may be undersampling with this setup - so am I imaging with a 60mm F/1280mm scope, or a 200mm F/1280 scope?

Michael

[David Smith]

You're imaging with a 60 mm scope @ 1280 mm focal length. I don't know enough about the toucam to comment on under / over sampling but never found it a problem. Are you taking single frame "stills"? If so you will get better results taking a 1000 frame avi and then stacking the best 5-10% in something like Autostakkert.

[michael8554]

Stills, and avi's stacked in AutoStakkert.

Michael

[michael8554]

Well I obtained a used Kendrick full aperture filter which uses Baader film.

Tried it today and resolution was much much better.

I'm surprised as there are a number of posts on SGL of results using sub-aperture, and resolution didn't seem to be a problem, perhaps I had had a day of very poor seeing....

I tried two cameras today:

Canon 450D using "EOS Movie Record" to make 20fps AVI's of the Live View X5 (848 x 568 pixels)

Atik 2HS Mono (Toucam Pro based), 10fps (640 x 480 pixels)

The results from the EOS were best.

I expect if they were on my 70mm Ha PST stage 1 the mono Atik would be the winner.

Michael

 

[michael.h.f.wilkinson]

I have always used my 8" SCT in full aperture for solar. Works a treat

[ArmyAirForce]

A green filter or Baader Solar Continuum Filter ( with UV/IR block filter ) will improve a mono image further. For Sun spots and granulation, green light gives the clearest view. The Baader Solar Continuum filter only lets a small part of the green spectrum through, but as you can see from my test, a green filter from an RGB set gives the next best detail.

[michael8554]

Interesting Stephen,

Have I got this right? Your images show the effect of R, G, and B filters on a mono camera?

Do you have a Baader filtered image for comparison please?

What  difference does the UV/IR filter make? 

Thanks

Michael

[ArmyAirForce]

These comparison shots were taken before I got a Sol Cont filter. They were all done with an ASI120MM camera which doesn't have any IR/UV filtering built in to the camera. With the Sol Cont filter, it leaks in IR and so you need to use a good IR block filter with it or the IR blurs the image. I don't have an identical image, as I said, these were done before I got it, but I have this one taken with the Sol Cont and IR block with the same ASI120MM camera on an Evostar 80ED refractor.

[ArmyAirForce]

This is a good article about green and sol cont filters - http://www.schursastrophotography.com/solar/Articles/solararticle3.html

[michael8554]

Thanks again Stephen - great images too.

The mono Atik doesn't have a IR filter, but I think I have one somewhere.

I'll read that article in the morning.

So should I use my Astro-modded 450D, or my wife's unmodded 1000D, for white-light? 

Don't tell her.....

Michael

[ArmyAirForce]

I think the standard unmodded cam will be better. Red light from the modded camera isn't the best light to use. With a standard DSLR, you have two green pixels to every one red and blue, and as I've shown, green is the colour to go for. Plenty of time to experiment though.

 

[michael8554]

Read the article, the effect of the CS-G, and the Baader Continuum + UV/IR, was hard to see in the full-disc images, apart from the limb darkening.

The effect in the closeups was quite marked.

The Baader seems to be a bargain in comparison to a CS RGBY set.

Which ordinary G filter would you recommend?

Michael

[ArmyAirForce]

Not sure about normal green filters. I just used the green from my ZWO RGB imaging filter set to start with as I don't have any visual filters. Of course any filter is going to work best with the mono camera. The DSLR only has two pixels out of every four that will pick up green, so any single colour filter is a little wasted on a DSLR sensor. For the price of the 1.25" Solar Continuum and an IR/UV block, I would just go for those as they can be used for visual and imaging.

Edited March 22, 2016 by ArmyAirForce