To prevent purchasing another piece of dedicated equipment, I am thinking of setting up one barrel of my APM 100mm bino with a Daystar Quark Chromosphere filter. As follows:
APM 100 ED bino (f/5.5) – owned (one barrel capped)
1 – Daystar 100 x 130 ERF - $695
1 – Daystar Quark H-Alpha Chromosphere - $1295
1 – Tele Vue 40mm Plossl E.P. - $155
1 – Tele Vue 24mm Panoptic E.P. – owned
1 - Tele Vue Sol-Searcher Finderscope - $45
1 – Daystar Battery Pack, 5V 30Ah $105
So, I am looking at about $2500 for a 100mm 0.5 Angstrom H-Alpha telescope? Maybe a $4000 savings over a similarly spec’d dedicated 90mm H-Alpha scope?
Specs with the Quark and my APM 100 bino (using S&T online calculator):
f/23
0.7 TFOV
24mm Panoptic (68 AFOV) 96X, 1.0mm exit pupil
40mm Plossl (43 AFOV) 58X 1.7mm exit pupil
I respectfully ask this forum, is there anything inherently wrong with this setup for visual and outreach usage? Thanks.
Hi Roger,
While your approach to getting an idea of value for money relative to what you already have here makes sense, there's a few key elements that are not accounted for that were already mentioned above, but I'll reiterate so that you can really take a moment.
The FWHM of these filters is largely meaningless, the only assumption that can sort of be trusted is that the more narrow the bandpass, the more contrast there should be on the CWL, but it's just not always true and single stacks will always have photosphere leaking through reducing contrast (you will always see it in the form of a double limb even at 0.3A with a single etalon); it's important to simply look more at the transmission profile and the wings around the CWL as that's where all the work is being done to remove them from the system. A single stack 0.5A etalon compared to a 0.7A double stack etalon will be strikingly different visually and when imaging, the 0.5A rating has nothing to do with it, the key thing to focus on here is to ignore these two numbers at least at this stage of things and instead focus on there being 1 or 2 etalons as this is far more meaningful to what you will get as an end result without knowing any numbers (and those two numbers are entirely arbitrary in my example).
Again that number is largely just not meaningful, but it's easier for marketing and people to talk when there's a number and it has a linear relationship with some context. In this case, its mostly marketing (I say that loosely, it has meaning, but not much at the end user side of things). You may buy a filter that is rated for 0.5 or 0.7 A and then put it in a F20 telecentric light cone (referring to any of these mica spaced system from Daystar or Solar Spectrum) and not realize that the filters were rated based on their F50+ performance and not F20, F30, etc, and so they will perform poorly for that rated value in that context.
Uniformity and finesse are two major properties of these filter systems (etalons) that ultimately matter way more than the FWHM bandpass value. These are not going to be given to you. They are the things you find out about after the purchase and only after some experience. I'm going to go out on a limb and imagine you care a lot about quality and not just quantity and value. A Quark is a high value filter with pretty commonly low quality uniformity and finesse. A lot of people will claim their Quarks are great and that's fine, but almost all of them have poor uniformity and this is so much more important than a FWHM rating. There are a few cited Quarks out there that are referred to as being very good, but what's not talked about is how they were lucky and cherry picked, and that they are not the expectation of a Quark at all and like many entry class filter systems, they cycled through several of them to find one that was even remotely good. The end user experience is highly effected, it's the difference of seeing an entire in-band FOV of your subject compared to seeing a partial in-band FOV where one area or several areas are brighter with lower contrast than others and it has a patchy look for a dark to light gradient look. This is hallmark of low quality uniformity and if you care about quality this is the biggest quality property you would probably eventually come to focus on, after the initial honey moon period seeing h-alpha for the first time. This was not a cheeky statement nor a negative thing towards anyone if they felt targeted, this side of the filter system is just rarely talked about because there's absolutely no standard and there's no reports with practically any of the filters except research grade stuff to even begin to have any sort of basis for the discussion on this subject other than what essentially is experienced anecdotal user feedback and experience. But it's a profound thing in terms of quality. Many people think they have awesome filter systems because they're seeing h-alpha features, but then show an image and it's half on-band, huge gradients, patchy uniformity or straight up looks tilted, because most of them are poor uniformity. And uniformity is a difficult thing to achieve, you pay dearly to get close to having a high degree of uniformity and it's even more difficult and costly to have two etalons that are both equally uniform and have high finesse. It's largely a gamble at the entry price level that most people start at.
So this mainly comes down to your expectation for quality. If you want the highest value bang-for-buck single stack h-alpha experience with largest aperture potential that will work on gear you already have, you're already looking at the right things. But if you're more about high quality but still want to be conservative with value there are other things to consider. But instead of just throwing out products, it really should start with discussion as mentioned throughout this thread, because knowing what you're even buying is quite steep with these filter systems and none of the important information is actually shared by the distributor/seller on these crucial concepts (they're way too difficult to market for the cost). There's always gamble with these filter systems, again, because there's no standard at all on uniformity and the FWHM rating is largely meaningless. The most important two things you should focus on if you care about high quality results and experiences are uniformity of the filter system and the support for the filter system.
And then finally:
1 – Daystar 100 x 130 ERF - $695
1 – Daystar Battery Pack, 5V 30Ah $105
The Daystar ERF is not worth buying, it's also not needed at all here at 100mm. Daystar ERF are just colored glass, they're not optically flat and they don't even block much heat, they let through tons of IR. Think about what happens when you put a non-optically flat thick piece of colored glass in front of your high quality optics? The overall system will have the wavefront potential of whatever the worst component is. Also it absorbs heat, it's not dielectically coated, so you also have a hot piece of non-flat glass in front of your optics. Don't buy this Daystar ERF.
A simple dielectrically coated UV/IR cut filter or red imaging-class filter will handle all your ERF needs here for pennies.
Also, the battery pack is not special, you can get any lithium based battery pack with USB online for half this price or less and do the exact same thing. No special numbers to know. Just USB, a power bank for phones or tablets handle this.
As for eyepieces, keep them very simple. Plossls are good. Very wide AFOV eyepiece designs will not be ideal (usually). There's nothing to see beyond the limb in these filters systems other than some prominences, so you don't need wide FOV. Focus instead on highest contrast designs, simple optics. Also a 40mm plossl is ok, but I would suggest a 32mm instead for the typical reasons you'll find anywhere else with respect to the 1.25" barrel and its parameters.
Binoviewers are the #1 visual accessory to consider. Very much a game changer and a much more relaxed squint free experience. But, binos are less friendly to outreach so maybe single eyepiece for outreach use.
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You mentioned outreach and using what you have. Using a 550mm focal length with a Quark will not give you a full disc FOV with room to spare for prominences for an outreach visual setup, it will only show higher magnification partial disc FOV. I will say that your current scopes are fine for this use but I would suggest a different route. I would instead suggest a front mounted full aperture etalon (such as a Lunt 60, this can be double stacked later if you wish) with a mounting cap for one of your refractors, and a 12mm blocking filter where the diagonal would go. That will give you a very good more uniform disc image and can still take as much magnification as your seeing can handle and has no electronics to tune or operate it (unlike a Quark that needs electronics and takes minutes to tune between values and parts that fail over time; doing outreach you know how fussy this gets). The other refractor in your bino setup, I would put a 2" Herschel Wedge with a Continuum filter or similar so you have the two most common views of the chromosphere and photosphere side by side for visual study (or imaging). You'll get two equal disc image size discs in chromosphere (that can be double stacked for best contrast eventually if you want) and photosphere so you can see and study the primary visual structures and your guests can see both discs at the same time from one setup to learn more about what they're seeing and why.
Very best,
Edited by MalVeauX, 05 June 2023 - 12:47 PM.
