Coronado PST - monochome red?

[Stargazer_00]

Hi all,

My dad recently purchased a new Coronado PST (at summer prices!) and I finally got to look through a dedicated h-alpha scope.

I was, I must say, a little underwhelmed. It seemed to be quite hard to get a good, satisfying view through it and to my surprise the image was basically just red and black. I was expecting to see a range of colour from yellow through orange to reds all at the same time, like the photos you see everywhere.

Is this possible with visual? sure the thing shows proms, which are nice, but other than that it's just like white light solar. Little discernable surface detail, about equal to white light with a baader SC filter. See some 'cracking' on the surface, not much else. Sunspots are much better in white light.

it's pretty much just those proms, which are good I admit, but in just red/black it's a little underwhelming.

I'm hoping that there is something really simple that we need to do to get the expected views. Or maybe that's how it's supposed to be, I dont know?

[Zakalwe]

You will only see red. The PST strips out all other wavelengths bar from the H-a wavelength which sits in the red part of the visible spectrum. The colours that you see in images are false colours that have been added in post-processing.

Your eye takes a while to become "attuned" to picking out the detail. Plus, the seeing can make a difference (no different to viewing the Moon or a planet...for fleeting moments the seeing clears up giving a crystal clear view). Plus you have to tune the Etalon to get in "on-band".

You will see a LOT more surface detail in comparison to white-light, when you get it right.

Stick with it.

[nytecam]

The hydrogen alpha 'filter' in the PST and all similar solar scopes is necessary to isolate features on the solar surface. This monochromatic red view and is normal and other colours won't be seen - that's life.

The fact you've seen little of nothing on the sun and haven't mention the prominences [red clouds] on the sun's edge [=limb] suggests you haven't tuned the scope by turning the collar immediately before the black box at the bottom of scope slightly back and forth for the best views. I've has my PST [+ PST CaK version] for a long time and the views can be spectacular. Good luck;-) My old PST webpage [and what can be seen!]... http://home.freeuk.com/m.gavin/pstmg.htm

[Stargazer_00]

Thanks for the reassurance guys. I have seen the proms, and they are sweet. I have tuned the etalon and can see how it brings the proms into perfect focus/view. It is a nice scope for sure. I'd like to have higher magnification with larger exit pupils of course , but I guess that's what you have to spend thousands to get

[allcart]

try different eyepiecs, and maybe a x1.6 barlow lens. Take a while to get accustomed to the views. Its like looking at Jupiter. The more you look, the more you see.

[astrosathya]

Hi Graham,

The PST as we know is only a 40mm aperture scope. You could try the 66deg wide angle 9mm focal length eyepiece sold by various brands like ascension, william optics, sky-watcher and these work very well with the PST. The barlow will increase magnification but at the cost of field of view.

Regards

[lukebl]

I've tried various eyepieces with mine, but I have to say that the stock 20mm one (which comes with it) is the best for me. I find it gives a really nice sharp contrasty view, which compensates for the relatively small image size.

[DrRobin]

Hi,

Welcome to the world of solar Ha viewing. As others have already mentioned Hydrogen Alpha band is very narrow, in fact your PST is less than 1A wide and is firmly in the red spectrum, hence with the eye, you only see red. Most imagers use a mono camera and then add false colour later in the post processing stage. Many find that a shade of orange gives a more pleasing image than red and can help tease out a bit more detail, hence the reason for the range of colours in peoples pictures.

As regards magnification, the PST has a fairly small blocking filter (5mm I think) and this limits the field of view greatly, so really wide eyepieces just don't work all that well. The bigger the blocking filter, the more money you pay. For example a 10mm blocking filter will cost about as much as a whole PST.

My PST was great with a 20mm eyepiece, nothing wider was any good and when I tried a small focal length it was a little disappointing. I understand Televue and Baader Hyperion zooms work quite well on a PST, but I have no first hand experience.

The other issue with these type of scopes is the relatively small area that the sun's surface is correctly on-band, or correctly tuned, this is also refered to as the 'Sweetspot'. Some PSTs have a sweetspot that is big enough for the full disc and others don't, it is just pot luck. It is therefore the size of the blocking filter and how big the sweetspot is that determines how wide a view you will get.

The maximum amount of magnification is still limited by the 50x per inch rule, so you have about 1.5 inches, that indicates that the highest magnification is going to be around 75. As the PST is 400mm focal length you could go down to a 6mm eyepiece.

I hope that helps.

Robin

[Stu]

I've tried a number of eps in my PST and always come back to my TV 11mm Plossl. It's really sharp and more often than not is the optimum magnification possible. Occasionally I use a 9mm BGO for higher power but don't think it adds much.

Although the image is red only, I find that there is plenty of surface detail visible which you don't get with white light. Filaments and granulation are very clear, along with the usual sunspot groups. You tend to need a slightly different etalon position for the filaments vs granulation.

Cheers

Stu

[Stargazer_00]

thanks guys. I found my ES 82 degrees worked well in the PST. I quite liked the 6.7mm for looking at specific features and the 14mm for looking at the whole disc. It was pleasing, for sure, I was just expecting non monochomre - my dad is pleased as punch and get's his scope out at every opportunity. Based on what I've seen I probably won't pick my own PST up and I'll use his on occasion instead.

Can you let me know what a CaK shows compared to white light and H-alpha?

[DrRobin]

CaK is also narrow band, some of the same features that show up in Ha also show up in CaK. Although I haven't owned a CaK telescope from all accounts it is harder than Ha. Alexandra (aka Montana on here) wrote a very good guide to what can be seen in Ha and CaK, I have attached a link for the CaK below.

http://www.stephenramsden.com/SOLARASTROPHOTOGRAPHY/Observing%20in%20Ca%20II%20K.pdf

Robin

[nytecam]

Can you let me know what a CaK shows compared to white light and H-alpha?

Although as earlier quoted, I've a PST CaK I [due to yellowing of cornea through old age!] can't use it visually as there's nothing to be seen [for me] but my cam can held afocal to EP and I was well aware of this when I purchased it.

I videoed transit of Venus last year through my PST CaK

[paulastro]

As Robin pointed out, individual PSTs vary a great deal in what they will show. From what you say, yours sounds to be ok. I tried one (a new one) for sale at Kelling last Autumn and there is no way you could tune it to see prominences or any surface detail, easily the worst I have seen. Most show prominences ok and some surface detail, but this varies a great deal. Sometimes the image in the finder is way off, sometimes dead centre, it can be anywhere. More worrying is that some tuners come to a stop at one extreme when the detail is still improving. This gives you the feeling it may not be going far enough to show the view at its best. If you're lucky you will have one where the best tunning position is somewhere near the middle of the tuner's travel. Also, the contrast (the degree of blackness surrounding the Sun) can vary from black to varous degrees of pink.

Don't get me wrong, I love the PST and wouldn't be without mine, you just need to be a bit choosy and preferably view before you buy. I've seen examples which have out performed some Coronado 60mm and 70mm scopes. This is probably a combination of comparing a very good PST with poor examples of the 60 and 70. The one I have currently is excellent, the best of many I've every tried and as well as the prominences will show excellent surface detail in good conditions.

[Stu]

More worrying is that some tuners come to a stop at one extreme when the detail is still improving. This gives you the feeling it may not be going far enough to show the view at its best. If you're lucky you will have one where the best tunning position is somewhere near the middle of the tuner's travel. Also, the contrast (the degree of blackness surrounding the Sun) can vary from black to varous degrees of pink .

This can actually be fixed. You take the rubber grip on the tuning ring off and this exposes a series of holes. You can change the one which is used to fix the tuning ring and this gets the sweet spot for tuning more into the middle of the range. I've done this on mine and it works well.

Stu

[keithatrochdale]

As has been mentioned the 'seeing' varies from day to day. Too rarely do you get a really good day, but when you do it is worth the wait.

We have found the cheap Seben zoom eyepiece works really well and you can zoom in as much as conditions allow; seeing can fluctuate from minute to minute, so put in plenty of looking.

I also find a blocking screen very helpful (mine is made of cardboard) or a cloth over your head like the old photographers