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H-alpha for beginner with 8SE

Solar SCT Equipment
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#1 big bob

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Posted 26 October 2021 - 03:49 AM

Hi-

I am interested in trying H alpha viewing.  Most articles seem well beyond my knowledge.

I note that there are a fair number of scopes in the classifieds with widely varying prices (even for what seems to be the same 'scope).

 

My questions:

Can I mount a solar scope on my 8SE (with covers in place...) to allow automatic tracking? 

 

I reside near the ocean and believe a smaller aperture is preferred; is this correct?

 

Do these kinds of scopes come with eyepieces or can I use my std 1.25 or 2" eyepieces?

 

I presume that a bandwidth of 0.5 Angstrom is preferred; is this a fixed feature of solar scopes or do can a 0.7 Angstrom be updated in the future?

 

Are all (most) solar scopes in the classifieds "complete packages" or are there critical elements I should look out for?

 

I have way more questions, but let me start with these.

 

Thanks!

Bob

 

 



#2 vincentv

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Posted 26 October 2021 - 10:52 AM

 

Can I mount a solar scope on my 8SE (with covers in place...) to allow automatic tracking?

The SE mount will probably be overwhelmed by the weight. You can, however, remove the SCT and mount the solar telescope by itself. The SE mount has a "vixen dovetail". I believe in the celestron mounts you must go to the settings to enable the sun as a target.

 

 

Do these kinds of scopes come with eyepieces or can I use my std 1.25 or 2" eyepieces?

Solar telescopes use standard astronomical eyepieces. 1.25" is the by far the most common. The sun has a diameter of only 0.5 degrees so the wide fields of 2" eyepieces are useless.

 

 

I presume that a bandwidth of 0.5 Angstrom is preferred; is this a fixed feature of solar scopes or do can a 0.7 Angstrom be updated in the future?

Kinda, it depends. The angstrom measurement is common with rear mica etalons (like SolarSpectrum and Daystar) because they are very finicky to double stack. Basically you get one etalon and that's it.

Telescopes by Lunt, Coronado, etc can be double stacked. That is you add a second etalon to narrow the bandpass. Look for comments by user BYoesly in this forum to learn more.

 

 

Are all (most) solar scopes in the classifieds "complete packages" or are there critical elements I should look out for?

Since you mention "scopes" I'll stick to Lunt and Coronado dedicated scopes. There are 2 main components: etalon and blocking filter. Most of the time you'll see them as a package. Every now and then someone will offer an incomplete telescope so ask before buying. If possible try before you buy.


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#3 BYoesle

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Posted 26 October 2021 - 02:45 PM

Solar Hydrogen alpha detail is addictive, but the filters/telescopes are expensive. At $1000 you're usually at the "entry level." Unfortunately, even with the most expensive solar filter systems and telescopes, consumer-grade systems can have a great deal of variation in quality between manufacturers, and even within a particular manufacturers’ product line. I would always advise getting filters and telescopes with full money-back warranties, and if buying used get an ability to return the filter or telescope system if there is any question about quality or function.

 

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) H alpha etalons.  These can be used with stand-alone telescopes, and are generally the most expensive filter systems in larger apertures. Front etalons generally offer the most uniform image contrast for low power full-disc views, and especially imaging. But some manufactures can have issues with quality in which this may not be the case any longer.

 

Double stacking two filters can be used to improve 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 can 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 in the past which use tilting to tune the etalon could compound the sweet spot with “banding.”  These issues become moot with air pressure tuning, and 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), banding issues have been eliminated. 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, but the implementation is generally not as uniform as air pressure tuning.

 

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

 

3. Rear (focuser mounted) etalons.  These etalons generally require a 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 for reaching f30 +.  However, low power sweet spot issues may occur depending on the particular telescope used – especially if using an ordinary Barlow lens for amplification. As with internal etalons, these are generally moot for close up views and imaging. Tuning of the etalon is usually achieved by heating (and with Solar Spectrum filters heating and cooling), and thus these filters generally do not suffer from banding. Note: If considering a Quark, 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 shorter focal length telescope and/or a longer focal length eyepiece for full disc views, and contrast uniformity may not be so good, but again this is entry level.

 

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 have not had deterioration issues, although the Coronado’s have experienced blocking filter issues with premature failure of the Induced Transmission Filter, and the Lunt BG blocking filter 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 also subject to deterioration of the blocker and trimmer filters, and may require replacement and/or rebuilding after about 10-15 + years. However, Solar Spectrum has recently begun to use hard-coated blocking filters which promise greater longevity.

 

Filter bandpass can be difficult to address depending on filter location and implementation, and for the most part is meaningless. Generally a narrower bandpass is preferred over a wider bandpass for disc detail. However, most all single etalon systems have transmission profiles – no matter what the bandpass – that will allow some parasitic light from the photosphere to leak through, which decreases surface contrast.  Double stacking two filters can eliminate most if not all of this parasitic continuum. Prominences generally will not be very affected by the narrower bandpass, but overall image brightness is decreased due to the overall reduced filter system transmission.

 

Lastly, daytime seeing is very much a limiting factor compared to nighttime observing. 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 with some references in the Best of Solar Forum posts.

 

Also see Lunt’s blog post on internal etalons and issues with tilting versus pressure tuning.

 

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 etalon is best and more cost effective.  Double stacking should be high on a list of priorities for both visual and imaging performance if it is possible. In order I prefer two front mounted etalons, followed by a front and internal, and lastly two internal filters. Rear mounted filters are monolithic systems and therefore rather difficult to double stack, but this has been done.

 

Hope you may find this of some help.


Edited by BYoesle, 27 October 2021 - 12:10 PM.

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#4 MalVeauX

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Posted 26 October 2021 - 05:38 PM

Hi-

I am interested in trying H alpha viewing.  Most articles seem well beyond my knowledge.

I note that there are a fair number of scopes in the classifieds with widely varying prices (even for what seems to be the same 'scope).

 

My questions:

Can I mount a solar scope on my 8SE (with covers in place...) to allow automatic tracking? 

 

I reside near the ocean and believe a smaller aperture is preferred; is this correct?

 

Do these kinds of scopes come with eyepieces or can I use my std 1.25 or 2" eyepieces?

 

I presume that a bandwidth of 0.5 Angstrom is preferred; is this a fixed feature of solar scopes or do can a 0.7 Angstrom be updated in the future?

 

Are all (most) solar scopes in the classifieds "complete packages" or are there critical elements I should look out for?

 

I have way more questions, but let me start with these.

 

Thanks!

Bob

Hi Bob,

 

Bob Y already answered a lot. I'll add a little something to add some more pathway and discussion on this.

 

1) What's your max all in budget?

2) What's your mount?

3) What's your expectation (visual vs imaging)?

4) For a used solar scope, there definitely are things to look for, but no guarantee, so I always caution folk buying used unless you can physically look through it. And couriers can wreck etalons in mail.

 

Personally I recommend against trying to get a C8 or any mirror based optics to work for HA solar, unless you already have a lot of experience with solar to begin with. Using a mirror based optic already requires an energy rejection filter at the front aperture, which eats up any budget you have, and don't try to start with huge apertures unless you evaluate and can prove to yourself what your seeing conditions are because that's the absolute limit for this during the day. I would definitely avoid putting your budget into a small aperture masked energy rejection filter on an 8 inch aperture forcing a huge image scale, plus it only works with rear mounted HA filter systems which require electronics to even function and will not last forever and need maintenance and sometimes fixing (so support would matter a lot).

 

Personally for a tip toe in, a dedicated refractor based option is just going to be more bullet proof. I would put you on a smaller Lunt refractor without hesitation. Way less gamble on etalon quality. Great support.

 

Very best,


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