Lodestar-C with Ha 35nm filter

[DoctorD]

Hi

A great night and some new targets for me - looks like I'm getting to grips with the 35nm Ha filter.

All taken with Lodestar-C, Baader 35nm Ha filter, Lodestar Live, INED70 with AE x0.6 1.25" reducer (210mm effective F/L, F3.0) screen grabs showing display settings.

60s exposures with median stacking.

There's a strange artefact in the Flame/Horse Head Nebula and M78 which I think is due to internal reflections in the reducer, caused, I think, by local light pollution from a HP Sodium lamp - not evident in all the images. Or possibly from a  bright star.

All in all a great night.

Once again thank you Paul81 for creating and developing Lodestar Live!!

CS

Paul

[f15p5]

Very nice images Paul! Looks like you have it all figured out. Thanks for sharing!

Richard

[RobertI]

Good results Paul, the Ha filter looks very effective.

By the way i can't make the your attached pictures big enough to see properly, can you export images from LL next time so we can have a proper look?

Thanks

Rob

[RobertI]

Feel free to ignore previous remark, i realise now the point if screen grabs was to show the display settings.

[DoctorD]

Hi Rob

Thanks for the comments.

All the images are in my gallery - I like to do a screen grab so that it includes the settings so that people can see how I have adjusted the levels.

I think it may be an issue with how the gallery links are displayed.

CS

Paul

[PatG]

Great shots Paul, especially the Rosette and Cone. Nice FOV with that set up! What stacking settings do you use i.e. 'key frame control'  and 'output filter settings' on the stacking tab? 

Regards

Pat

[Martin Meredith]

Halpha working a treat! Of these, your Flame + HH5 is a particular favourite. You've captured the 'sheet' of the background behind the HH really well at the same time as keeping the head dark.

Martin

[DoctorD]

Hi Pat

Thanks.

The AE x0.6 reducer is working much better than my F6.3 SCT reducer with the INED70 and gives x0.5 reduction.

If I ocudl only work out what is causing the strange reflection or possibly vignetting  in the HH and M78....

Stacking set to median and Max Pixel to 12, output filter set to None.

5 x 60s darks.

CS

Paul

[Dave In Vermont]

I'm pleased to say the 35nm Ha from Baader is the newest one to surface - and the least expensive. But finding images taken through one is rather difficult. Your images come as a welcome surprise!

Thank you for posting these,

Dave

[Spacedout]

Nice shots Paul, well done!  Can I ask what this filter does roughly and is it for specific targets only?  I've not managed a decent Horse shot yet so this could be the missing ingredient

Cheers

Karl

[DoctorD]

Hi Karl

The filter isolates the Hydrogen Alpha emission line which is present in some emission nebula (at the red end of the spectrum - 656.28 nm wave length).

http://en.wikipedia.org/wiki/H-alpha

The 35nm refers to the width of the filter, the narrower the filter the less back ground light (e.g. light pollution or light from the moon) gets through.

You'll see filters as narrow as 7nm or possibly even narrower but these get really expensive.

The 35nm are one of the cheapest Ha filters about.

Here's a thread on targets suitable for Ha imaging:

http://stargazerslounge.com/topic/103581-hydrogen-alpha-imaging-best-targets/

CS

Paul

[Spacedout]

Thanks Paul, I think I'll get one and have a go.  I was using a Baadar Moon and sky glow last night and another cheaper version on the other camera and it did make a difference.  I had to go a little longer on exposure but I did some nice detail.

Thanks again

Karl 

[Dave In Vermont]

This may give you an idea of what it does with incandescent light:

It's quite a bit more selective than the Moon and Skyglow from Baader. But these 35nm Ha's are pretty new. Lot's of room to make unique discoveries with them.

Clear & Dark Skies,

Dave

[Merlin66]

Just as an aside....

I've been using the Baader 35nm Ha CCD filter for the last couple of years - as replacements for the failed ITF filters in solar blocking filter assemblies!!!

Works 100%.

[Spacedout]

Thanks Dave/Merlin,

This filter is now on the shopping list!  I wonder however how much better the 7nm would be as the price jump is not massive but would the difference justify it?  Sorry to hijack your thread Paul   All in the name of scientific research

Cheers

Karl

[NickK]

The main thing is to think about the light received by the CCD as the area under the graph.

A 35nm is good enough to avoid the main LP peaks (656nm where 35nm is, in theory, 17nm one side and 17nm the other). Although different filter models differ.

With 35nm you get more photons - although some is LP and some from other sources (moon light etc), the main contribution is Ha. 12, 7nm and 3nm all reduce the band of spectrum returned so the area under the graph is less but the amount of Ha is the same. The result is more contrast (although the image appears dimmer it should still have the same Ha level). However as the bandwidth of the filter reduces the price rises steeply. 35nm is a great, cheap, tool for EAA observing.

You should still get Ha in OSC cameras, although with an RGGB bayer you'll get 1 out of 4 pixels with Ha information. Other forms of bayer may provide a better return - however the sensor bayer does limit. This is where a mono sensor wins for narrowband. However for normal visual targets - the OSC speed to return a image is normally preferable.

Another option is using a broadband as a clipping filter for other forbidden lines - i.e. using green or blue to block any red (i.e. non Ha and reduce sodium) however the area under the graph will be far higher using broadband filters in this way.

Find a target - learn about the spectra in the target and you can the use and abuse your filters to bring out the best in EAA

[Spacedout]

Thanks Nick,

I've not done much with filters before so this information is a lot to take in but something I want to learn about so thank you very much for the detailed response.

Best regards

Karl

[NickK]

Thanks Nick,

I've not done much with filters before so this information is a lot to take in but something I want to learn about so thank you very much for the detailed response.

Best regards

Karl

I make it sound like a maths/physics lesson.. it shouldn't be (my parents were both physics teachers).. but it would help short cut some DSO/filter combinations!

[DoctorD]

Hi

Craig Stark of PHD/Nebulosity fame wrote an interesting paper on using line filers such as Ha with colour CCD cameras:

http://www.stark-labs.com/craig/resources/Articles-&-Reviews/LineFilterRecon_API.pdf

The CMYG bayer used in the Lodestar-C camera offers benefits over RGB matrix when used with Ha filters, although not a good as when used with a mono ccd.

Interesting reading!

CS

Paul

[NickK]

Indeed - CYMG would get two pixels out the four compared to RGGB. Note the Ye and Mg curve over the main sodium spectrum. They do not provide the same level of clipping (i.e. 40% of light from a sodium light is still around) hence the Ha filter is still needed - then you can use the Ye and Mg channels, the C and Cy channels at 20% could (in EAA noise levels) be additional noise rather than signal - although it could be that the Mg/Ye channel is used to produce a signal for alignment and filtering for an Ha target for the C/Cy channels (as everything is interpolated).

I note the relative response curves are valid in relation to their own graph - not valid in comparing between the two graphs.

[nytecam]

Great images Paul - interesting filter stuff from Nick:-)