Solar tests with QHY5

[jnp]

My first experiment at Solar imaging using a QHY5. This was also first light for my homebrew filter wheel (link here) and an opportunity to try out a cheap Calcium K filter (link here). The scope was just a DIY 90mm F11 achromat (Celestron Astromaster 90 lens) that unfortuately I hadn't got around to fitting baffles yet, so there's one area for improvement:o

I was surprised at the resolution of the QHY5 (compared with a DSLR) as I coudn't get the whole disc in, even with a 0.63 focal reducer.

I set the exposure time as fast as possible but I think this has introduced some vertical lines into the white light images (is this common?). They are less prevalent of the CaK as they needed longer exposures.

The yellow shots are taken with a green filter. The purple use the Calcium K but you all knew that.

Thanks for looking

John

[Montana]

A fabulous set of images John, I see you have been having a lot of fun

With the CaK filter, I possibly think that the bandwidth is not narrow enough to see the finer CaK details. Definitely you can see enhanced faculae but none of the plage around the active regions. Like hydrogen alpha you need a very tight and narrow band (hence the price). But there are definite hints there

Regards

Alexandra

[smerral]

Nice shots. Yes I agree with Alexandra about the CaK. Nevertheless, for a cheap filter it does very well.

[jnp]

Thanks for the kind and informative comments. I didn't appreciate that CaK filters can be as expensive as very narrow-band Ha!

My CaK filter is a genuine interference type filter. One side is deep purple, the other side is reflective. Does it make a difference which way around it is mounted?

I would like to know how it compares with other eyepiece type filters such as the Baader 1.25", which is advertised with shots where plage is visible. The Baader specifies "a sharp 8nm wide bandpass, centered at 395nm", but mine states "CWL 394+-2nm" but are we comparing apples and pears?

I intend to have another go as there is room for improvement, especially if i try it on my 8" newt.

Cheers

John

[Zul]

Nice Shots

[Merlin66]

For your filter the 394 +/- 2nm just means the position of the maximum transmission, not the bandwidth of the transmission curve. There may be other data you can check to confirm the width.

With interference filters, the "shiny" reflective surface should point towards the light source.

Some imagers are having success with a combo of the Baader Continuum filter and a IR cut-off, as well as a DSO OIII filter.

[markt]

Very interesting results John! The Omega CaK filter is a very good value and comparable alternative to the Baader K-Line, there really isn't much in it with them apart from the Omega has a lower transmission value. Are you using it in combination with some kind of ERF - eg Baader Solar Film (photographic)? It will work without, but by doing this you will be putting a huge thermal loading on the filter - the net result of this is likely the various coating layers could start to oxidise, essentially the same 'rusting' that has happened with Coronado blocking filters...

Regards the 'lines' on your images, i've heard of similar things before - though i'm not entirely sure what causes them; I know that is not much help but the good news is if you have Photoshop (I use CS4) you should be able to get rid of them using the 'De-Interlace' filter.

Either way, excellent results! I look forward to seeing more

[jnp]

First chance to have another go today. The baffles were added to the 90mm DIY achromat and the Cak filter is now pointing shinny side to the Sun. I think there is an improvement (is that a bit more plage showing?), but found focusing harder as the seeing was not as good.

By luck I found that using a Paul Rini 40mm eyepice as a focal reducer exactly fits the Sun's dic on a QHY5. (Need to sort collimation though).

cheers

John

Edit - Markt - yes I am using a DIY Baader Solar filter at the objective end.

[Merlin66]

Looking very good. Well done! ( I don't know about the P Rini eyepiece/ reducer though ;-) )

Look forward to your future images....