Full disc halpha HD from May, 31

[colmic]

Hi all,

come back from RAS 5 (Meeting of Solar french amateurs, 5 days). Weather was good and seeing fine.

Full disc with the Tak TSA120 + SM90 double stack + Barlow 2x Baader VIP + Grasshopper3 ICX674
ITF from the BF15 was removed. I gain a 2x factor in exposure!

Mosaic of 6 panes. Autostakkert 2 + Registax 6 + Photomerge + CS5
Images reduced by 50%

[jp-brahic]

Fantastic FD Michel!!!!:)

JP

[solar]

Nicely done.

[swisswalter]

Hi Michel

wonderful results. Do we need an ITF at all for Imaging ?

[gabrieli]

Michel

It's great to see your wonderful full discs again.

Lou

[Montana]

Truly magnificent

any chance of a full size version to savour the fine detail?

Alexandra

[colmic]

Thank you all.

Walter, no need of the ITF for imaging. I replace it by the Baader IR/UV-cut.

Alexandra, here is the full-size version:


And 2 wallpapers in 1920x1080 for your screens

[eroel]

Michel:
Superb full size discs.
What is the ITF?
Regards,
Eric.

[swisswalter]

Hi Michel

thanks for the hint regarding the ITF (induced transmission filter)

[marktownley]

Lovely shots!

I would use an ITF if I was you - will preserve the life of the blocking element of the blocker - this is a laminated filter too so can 'rust' if not careful because of thermal cycling - I will get some pictures up this evening to show what i mean...

[mattwastell]

A 5 day Solar camp - fantastic!
These are super DS discs - thanks for the records.

[swisswalter]

Lovely shots!

I would use an ITF if I was you - will preserve the life of the blocking element of the blocker - this is a laminated filter too so can 'rust' if not careful because of thermal cycling - I will get some pictures up this evening to show what i mean...

Hi Mark

very interesting remark. What do you unterstand under the therm ITF-filter? That is an end of the lesson question

[colmic]

On Astrosurf forum we have actually the same discussion
What i have understand:
- without ITF, the SWIR (above 2µm) are passing, and this is dangerous for our eyes (and perhaps for the lifetime of the blocking filter)
- Without ITF, i gain a 2x factor in imaging with double stack (4ms exposure without vs 8ms with the ITF)
- a simple IR-cut lets passing SWIR too (i don't know about the Baader IR/UV-cut)
- Beloptik sells a good-quality KG3 http://beloptik.de/en/left/if-uv-ir-cut ... ing-filter
- Maierphotonics sells a good quality ITF too http://maierphotonics.com/656bandpassfilter.aspx but i tested the one from Vincent (DSobserver) and it is a little brighter than the Coronado one, but darker than the IR/UV-cut.

[sullij1]

Stunning work, they really are beautiful images.

[marktownley]

Here is the frequency response of the ITF, you can see what it is and is not letting through...

Cor-BF151-log.gif (135.94 KiB) Viewed 2248 times

[Merlin66]

Eric,
The ITF filter is the pre-filter which usually sits at the front of the Blocking filter assembly.
The final filter (closest to the eyepiece/ CCD) is the final narrowband blocking filter.
I've been using a Baader 35nm CCD Ha filter as a ITF "replacement"....
The BelOptic UV-IR/KG3 also seems to work well.....

[swisswalter]

Hi Mark

coronado ITF's are very different to the LUNT pre blocking filter

[Merlin66]

Walter,
I don't have any Lunt equipment but am very interested in your comment....
Do you say that the Lunt pre-filter has a significantly different transmission curve from the one shown by Mark???

[swisswalter]

Hi Ken

yes, I will post a scan asap

[swisswalter]

Well here is what I found, two scans one from the front, one from the back. No difference

itfb1200named.jpg (71.28 KiB) Viewed 2227 times

[marktownley]

I'll put money on it being one of the Schott BG family http://www.schott.com/advanced_optics/e ... ng=english

[swisswalter]

Hi Mark

as reported earlier, the filter is a stack of two identical plates.