Baader D-ERF or Lunt ERF?

[OlegLviv]

Hello friends! I have a plan in a future modification my 152/f5.9 telescope and wants will buy ERF filter and put inside ERF because with my modification can't screw a 2 inch filter (Baader 35nm or UV/IR CUT) in front of the etalon and ERF full aperture ist expensive for me....

Therefore, I have a question, what is the minimum erf size of 75 mm or 90 mm or 100 mm that can be installed in the diaphragm of the refractor?

And second question about brands ERF? (baader vs lunt)

Thank you!

[pupak]

If my information is correct, D-ERF contains dielectric reflective layers and hardly absorbs heat. Lunt's ERF is red glass with an IR coating so it absorbs more heat. I know two colleagues who have been running an AR150 for a long time with a 53mm ERF from Lunt in a combination of 2" H-a 35nm. This is a photographic mode, not a visual one.
I would be afraid of it myself, but they have been running it that way for several years and have had no problem. It is important to have the correct slope of the filter to avoid reflections.

[marktownley]

For a refractor that size and that fast you should mount the largest one you afford internally, the bigger the better!

[christian viladrich]

Regarding optical quality, my 160 mm D-ERF was measured to lamda/9.6, which is excellent :

http://astrosurf.com/viladrich/astro/in ... /tests.htm

Of course, it comes to a cost.

I haven't seen any measurement for Lunt ERF filters.

[OlegLviv]

Thank you for answers!

Tell me about PST etalon all pst etalons have 1A or Is it possible to have less?

I bought 152/f5.9 If will be buy Baader Glasspathcorrector 1:1.7 for Baader and put front my pst etalon will be F10 and its good result? (PST MOD 2)

Thank you!

[marktownley]

Thank you for answers!

Tell me about PST etalon all pst etalons have 1A or Is it possible to have less?

I bought 152/f5.9 If will be buy Baader Glasspathcorrector 1:1.7 for Baader and put front my pst etalon will be F10 and its good result?

Thank you!

I think it will work well!

[OlegLviv]

Thank you for answers!

Tell me about PST etalon all pst etalons have 1A or Is it possible to have less?

I bought 152/f5.9 If will be buy Baader Glasspathcorrector 1:1.7 for Baader and put front my pst etalon will be F10 and its good result?

Thank you!

I think it will work well!

Tell me about PST etalon all pst etalons have 1A or Is it possible to have less?

I mean like this a photo 1.25 but 1.7!

[marktownley]

As with all etalons there is much variance between them, some are good, some not so good. It's a case of either dropping lucky when you get one or buying several before you get a good one. I did the latter.

[OlegLviv]

As with all etalons there is much variance between them, some are good, some not so good. It's a case of either dropping lucky when you get one or buying several before you get a good one. I did the latter.

I remember i have Powermate 2x 2.0 can use in a front etalon PST and will be have f11?

Its tru that PST etalon USA better than PST etalon Made in Mexico?

Thank you!

[christian viladrich]

As said by Mark, there is a lot of variance in PST etalons.

I measured an excellent one at 0.34 A FWHM. His owner told me it was an "old generation" PST.

The other one was at 0.60 A FWHM. Not bad.

These are only two measurements. This is far from a statistics.

http://astrosurf.com/viladrich/astro/in ... lters.html

[OlegLviv]

Tell me about F with Etalon!
TS 152/5.9+Baader Glasspathcorrector 1.25=F7.4+Powermate 2.5x=F18.5 ist less for air space etalon???????? Lunt 50 mod!
TS 152/5.9+Powermate 2x 2.0=F11.8 +Powermate 2.5x=F29.6 its normal for air space etalon???? PST Stage 2!
Is my theory true?
Does this apply only to telecentric?

Because as for me Lunt 50 F7 will be better mod than Pst Stage 2 because F7 not F10 ?

Thank you!

[pupak]

I'm afraid it won't work for you with the 1.25 focal shift. This is an optical element that only shifts the focus but does not change the beam angle. It's not Barlow. It behaves similarly to a pair of lenses in the etalon. These will also shift the focus but maintain the beam angle. Correct positioning in the optical path is important for the Lunt etalon. F is not so critical.
Today I tried the AR150/F5.9 combination with the LS80 etalon, TV5x Powermate (F30) and Quark combo. Photos are in the Solarchat section. The sweet spot seems acceptable.