18 replies to this topic

[jag32]

I am searching for a good H-alpha solar filter setup that I plan to use on my Takahashi FC-76DCU and a TSA-120.  My budget is anything up to $1,500 and I prefer to buy a standalone etalon filter setup similar to the Quark as opposed to a whole separate scope (i.e. Lunt, Coronado, PST).  I've seen the option offered by Baader, but was wondering if there were other standalone H-alpha solar filters besides the Quark in the under $1,500 price range.  Thanks!

Edited by jag32, 11 July 2017 - 06:24 PM.

[BYoesle]

Solar H alpha is addictive, but the filters are expensive, and at $1500 you're at the "entry level." However, this is far better than when I started out in solar H alpha. Get as much aperture as you can afford, then double stack. A high-quality front ERF is usually better than an internal if you can afford it - make sure it has an IR blocking coating (Lunt or Badder). I would consider increasing your budget to $2000 and consider front etalon/blocking filters from Coronado or Lunt. The higher quality DayStar and Solar Spectrum filters and an appropriate ERF (which I also would consider for use with the TSA-120/Quark) will be even more expensive. If you intend to be a serious H alpha observer/imager, then you have to spend accordingly. If you only want to be a casual H alpha observer/imager, then the Quark is for you.

If considering a Quark, I'd get the Quark Chromosphere, DON'T BOTHER WITH THE PROMINENCE VERSION - you'll see prominences just as well with the chromosphere model, and disc contrast should be better. Due to the built in 4.2 x telecentric, you'll generally need a longer focal length eyepiece for full disc views, and contrast uniformity may not be so good, but again this is entry level.

 

Here's my tutorial for those just starting out into the world of solar H alpha - H alpha filter systems generally can be classified into three categories:

1. Front (objective mounted) etalons.  These can be used with stand alone telescopes, and are generally the most expensive filter systems in larger apertures. Front etalons usually offer the most uniform image contrast for low power full-disc views, and especially imaging.

Double stacking two filters can be used to enhance contrast (the second etalon usually requires some additional tilt to remove "ghost" reflections).
These filters are made by Coronado (Meade), Lunt, and SolarScope. SolarScope also sells dedicated solar Ha telescopes with front etalon(s).

2. Internal etalons.  Cost concerns resulted in placing a relatively smaller air-spaced etalon in collimating lens optical system within a larger aperture telescope, and these perform almost as well as front mounted etalons as far as image contrast uniformity. Some models are more subject to circular “sweet spots” with good contrast, while the contrast falls off outside the sweet spot. Some models which use tilting to tune the etalon will compound the sweet spot with “banding.”  These issues become moot with higher power views and narrow field imaging, as the whole view or image is generally within the sweet spot.

With the Lunt pressure tuning systems (which eliminates tilting for tuning), many sweet spot / banding issues appear to have been better controlled, if not eliminated in some models. Pressure tuning is the equivalent of changing the temperature in the DayStar and Solar Spectrum filters.  Coronado introduced “rich view” tuning, which involves mechanical pressure to avoid the disadvantages of tilt tuning.

Coronado and Lunt produce these designs for their dedicated solar Ha telescopes.

3. Rear (focuser) mounted etalons.  These etalons generally require a native f30 optical system or greater (using an aperture stop Energy Rejection Filter) to perform optimally. The use of telecentric optics can be used in faster optical systems.  However, low power sweet spot issues may occur depending on the particular telescope used. As with internal etalons, these are generally moot for close up views and imaging. Tuning of the etalon is usually achieved by heating, and thus these filters generally do not suffer from banding.

DayStar and Solar Spectrum make these filter systems.  DayStar also markets complete telescopes designed around their filter systems.

Another issue that should be mentioned is the deterioration of the filter. The air-spaced etalons used in the Coronado, Lunt, and SolarScope systems generally do not have deterioration issues, although the Coronado’s have experienced blocking filter issues with premature failure of the Induced Transmission Filter, and the Lunt BG element has had some cloudiness issues as well. Deterioration of the blocking filter’s trim filter has not (yet) become apparent for these systems.

The solid spacer etalons used by DayStar and Solar Spectrum are subject to deterioration of the blocker and trimmer filters, and may require replacement and/or rebuilding after about 15 + years. However, Solar Spectrum has recently begun to use hard-coated blocking filters which promise longer longevity.

Most all single filter systems will allow some parasitic light from the photosphere to leak through, which decreases surface contrast.  Double stacking two filters will eliminate most if not all of this parasitic continuum. Prominences generally will not be affected by the narrower bandpass, but overall image brightness is decreased due to the overall reduced filter system transmission.

Lastly, for visual use apertures over 150 mm generally will not increase resolution due to daytime atmospheric conditions (but will help image brightness for the rare moments of good image steadiness). For imaging, use of frame selection and stacking software can enable larger apertures to be of significantly greater benefit.

You may want to familiarize yourself with how etalons work:

http://www.cloudynig...-etalon-basics/

You will also find Colin Kaminski’s articles of great interest:

http://www.designeri...nArticlePt1.pdf
http://www.designeri...nArticlePt2.pdf

Also see Andy Lunt’s excellent blog on internal etalons and issues with tilting versus pressure tuning:

http://luntsolarsyst...l-and-internal/

My personal recommendation is that for full disk views and imaging, a front mounted etalon system is the best for its superior contrast uniformity.  For close up views and imaging, a large aperture scope with an internal or rear mounted system is best and more cost effective.  Double stacking should be high on a list of priorities for both visual and imaging performance.

Hope these 3 cents is of some help.

[SeymoreStars]

Excellent advice as always Bob. You a real asset to this forum, steering people in the right direction. I hope the fires subside and you get back to "normal" life.

[JPKellysr]

How about double stacking a Quark? I suppose one can just add a front mounted filter to do so?

 

JPK

[astroflak88]

What i do is put a polarizer at the eyepiece after the quark and greatly increases contrast.

[JPKellysr]

I will try that. I have been using a Baader Moon & Sky filter which also increases contrast, but I have a varible polarizing filter that might work better.

 

JPK

[MalVeauX]

I am searching for a good H-alpha solar filter setup that I plan to use on my Takahashi FC-76DCU and a TSA-120.  My budget is anything up to $1,500 and I prefer to buy a standalone etalon filter setup similar to the Quark as opposed to a whole separate scope (i.e. Lunt, Coronado, PST).  I've seen the option offered by Baader, but was wondering if there were other standalone H-alpha solar filters besides the Quark in the under $1,500 price range.  Thanks!

I assume this is for visual only?

 

If that's the case, I would actually not use a Quark. It works, and is excellent for it's cost, but I feel like its a lot better as an imaging device than a visual device, from a comfort factor. If you do, however, go towards a Quark, go for the Quark Chromosphere Combo version, so that you can control the FOV a lot more by providing your own powermate instead of the regular version that has the 4+x internal barlow.

 

Otherwise, like Bob pointed out, I would look to the stand-alone front mounted etalons. You simply won't be getting one that is 80mm aperture or more to match your scopes for your budget. Instead, you'll be looking at maybe a 60mm front mount for your budget. Unless you can find a used 80mm front mount right at your budget. Odds are not good there though, they rarely come up for sale. So more likely is going to be to find a 60mm new or used (front mounted etalon) with a blocking filter. Or getting it new (Lunt for example), in terms of your budget. If you can increase your budget a little, you may be able to squeeze in more aperture, but as aperture increases in HA the cost drastically skyrockets. A brand new 60mm front mounted Lunt etalon for example is literally right at your budget. 80mm or more quickly gets into double that price (100mm being $4.5~5k+).

 

For your budget, used is one way to get a lot more for your money. But, now's not a good time to buy, everyone will cling to everything until after 8/21 next month. Then maybe some will hit the for sale forums, because of the eclipse, and the very obvious solar minimum going on for the next decade, a lot of HA stuff will probably go up for sale I imagine by the end of this year.

 

I use a PST for my HA visual of the sun, despite having a 120mm aperture refractor with a Quark. It's just way more comfortable to look through the PST and see the detail both on surface & prominences, with lots of nice eye relief, no black outs, no tunnel vision. It's hard to look through my 120mm + Quark, the magnification is high, it needs tracking just to do visual (and of course image), and it requires really careful eye placement to get the view without black outs. So the PST is my visual grab & go and doesn't require tracking; it's a pleasure to use.

 

Very best,

[RickV]

Bob, thanks for that excellent summary tutorial in Post #2... should be a Sticky.

Marty, thanks for rounding out the info from a user 'comfort' stand point.

Superb!

[BYoesle]

 

What i do is put a polarizer at the eyepiece after the quark and greatly increases contrast.

Using a polarizer or ND filter (or a passing thin cloud) will reduce retinal saturation and decrease image brightness - which gives a perception of increased contrast. But simply decreasing brightness will do nothing to remove out-of-band parasitic continuum, as occurs with placing two narrow-band filters in series (although this also will decrease image brightness). The presence of parasitic continuum will therefor still manifest itself, which can easily be shown with appropriate imaging - try it for yourself... ;-)

[David D.]

I respectfully disagree with Malveaux about comfort. The view for me in a PST was very tight. Eye placement was finicky. The quark seems so much more comfortable. 

[TerryWood]

Regarding the PST, my own experience mirrors Malveaux's. I wonder if it just has something to do with each individual person's eyes. Through my right eye the view through the PST is great, very comfortable, with no blackouts. But if I use my left eye it's quite different, being difficult to find the right position to get a good view without blackouts, and when I do surface detail doesn't pop like it does through my right eye. Whenever I'ved used my Daystar .6a filter with my 80mm refractor proms look fantastic, but I've never had a good visual view of surface details. But, as soon as I place the mono camera in the eyepiece and watch it on the laptop screen the view of surface and proms is usually amazing (depending on the seeing conditions). V/R Terry

[DAVIDG]

 When it comes to a PST you should  check the alignment of the penta prism since in my experience it is very common to have them out of alignment . This can cause the issues people are having with viewing angle and eye placement.  

   Here are two pictures that show the prism out of alignment and correctly aligned.

 

                   - Dave 

 

 

[paulsky]

DavidG. ,

If for example I bought the PST:
- First of all, how would I know that my unit has this `problem? I mention it because I'm not an expert and maybe I would not know very well if the image is like this or that it has this defect (for my serious)
-In the second place, could I "easily" fix this or would I have to send it back to Coronado?

Thank you very much for your clarifications and opinions
Best regards
Paul

[DAVIDG]

 The easiest method to determine if your PST has  a misaligned prism is to just remove the side cover and look at it. It is a pretty simple fix as well. The glue that holds the prism in place is flexible. You SLOWLY rotate the prism back into alignment. You may have to go past the alignment position and let the prism relax back into place. Once it is in correct alignment, it usually will stay there. I did the prisms on three of my PST , 5 years ago and they are still aligned.

 

                - Dave 

[paulsky]

Thank you Dave for your kind reply.

Regards,

Paul

[je2000]

I look through double stack Lunt with a Televue eyepiece. I could barely see the sun. Too red. I am L-cone deficient. Anyone else? I figure monochrome imaging is my ticket with a Quark and an 80-100mm refractor.

[Tom Masterson]

I have the Lunt 50mm front mounted etalon bf1200 combo as my quick-look setup instead of firing up my larger heated rear etalon unit. Despite owning the higher resolution unit, I am very pleased with the 50mm Lunt and it's performance. The views are very sharp and contrasty. Unfortunately, you'll have to get an adapter made to mount the etalon unless by some slim chance the threads match the front cell of your Tak. Depending on the cost of an adapter, this keeps you very close to your budget cap. There's always the used market too which can save a few bucks.

[BYoesle]

Or find a local trades school with a machining technology program and it could be a student project... Pizza and pop are always appreciated. 

[BinoGuy]

I don't have a Quark, but I do like tuning the etalon on my ss PST to see if different details are visible.  As I understand it there is a delay with the Quark while it changes temperature.