Coronado PST Solar Scope - First Light

[Poita (Peter)]

Well, I thought I'd start a thread about my experiences with a Coronado PST from a total Noob perspective, I'll update the thread as things happen!

I purchased a 2nd Hand PST from an IIS member, it arrived today in its case with 20mm eyepiece, lens cap, and nothing else.

Clouds dutifully rolled in to completely obscure the sun.

I was surprised how small it is, and almost ridiculously lightweight. It looks a bit American/cheesy with it's golden tube and oversized PST logo on the base, but looks pretty well made.

It has what looks like 2 standard tripod threads in the base for mounting the scope.

The lens cap has a warning to read the manual before use. Also included was a handwritten warning from the previous owner, along the lines that this scope will do little else than get me hooked and make me purchase a solarmax 60!
Of the two warnings, the second one was probably the most important!

I dutifully downloaded a copy of the manual and had a quick read, with the intention of not accidentally burning a hole through my retina and cooking my brain.

Manual perused, the clouds parted briefly, so I lent the scope against the kids trampoline for support and pointed roughly towards the sun. After swinging it around a bit, the sun suddenly filled the eyepiece.

At first, the image seems to be a featureless, but very crisp bright pink circle that fills the eyepiece. Then after a few seconds, your eye adjusts and the sunspots are surprisingly sharp and clear. A few more seconds and the prominances are visible, albeit faint compared to the disc of the sun. Some surface detail was also visible.
Bear in mind that this is all happening whilst hand-held!
I was instantly hooked, but sadly had to pack it up and go back to work.

I will be mounting it onto a tripod tonight and take a proper look tomorrow.

First thoughts:
1) Solar is instantly addictive, unlike planets and nebulae etc. you don't really know what to expect as one hasn't been inundated with as many images over the years.
2) You get used to the 'pink' very quickly, but I wish it was yellow
3) The image is very clear and intriguing, but I can see why people would want a larger scope to be able to get higher magnifications to bring out the details.

Anyway, that is my 2 minute look at the PST, I'll post more as I get to use it more. Hopefully a perspective from a beginner will be helpful, I'll try to answer any questions I can.

-Peter

[scagman (John)]

Hi Peter,
congrates on the PST and thanks for the report and looking forward to reading more as you go.

[naskies (Dave)]

Hi Peter, thanks for writing up your experiences. As a fellow newbie, it's great to hear what that first experience is like

Dave

[Barrykgerdes]

Hi Peter

Firstly there is another thread "Imaging with a Coronado PST" in the equipment discussions. It is worth reading.

Even though the PST is entry level for solar viewing it is capable of very good results when set up with a good mono CCD camera (don't worry about colour the PST already has a tunable filter.)

It can be used on a simple mount for visual purposes but if you want to do serious photography a tracking mount is needed and a program that can make mosaics . I have a HEQ5 but some are getting excellent results with EQ3's and EQ2's that have RA drives that can be pressed into solar rate tracking.

Barry

[Poita (Peter)]

Thanks Barry, I've been following that thread with interest as I intend to have a go at imaging down the track.

I managed to come up with a spurious reason to get the art class I teach in the afternoons to all take a look through the pst, which let me get another look in

This time it was mounted on a manfrotto jr tripod. The built in finder on the pst makes finding the sun really easy, so we were set up and viewing in three minutes.

With the stable tripod and clear skies the views were much better. The prominences were really clear and easy to see, as were the sunspots. The focus with the included eyepiece could only *just* be reached, but you could see the lovely textured surface of the sun. It is a bit like viewing galaxies though, the detail is clearer in averted vision.

Although it fills the eyepiece, the disc of the sun feels very small, feels about the same as if you were just looking at the sun with great sunglasses.

Will try out some higher powered eyepieces tomorrow and see how it goes.

[Poita (Peter)]

I tried my various eyepieces today with the PST, and none of them can achieve focus. I tried the nosepiece barlow that came with the WO Binoviewers as well, but no go.
In fact the included eyepiece only *just* achieves focus.
Mine is one of the 'blue' PSTs, so apparently can't do the simple spacer mod to achieve focus with standard eyepieces.
Apparently there are ways around it, I'm just reading up now on the various methods and I'll see how I go.

[Merlin66 (Ken)]

Peter,
Which eyepieces were you using?
I normally just use the ol' TV 10.4 plossl which gives great views.....
The spacer section can be removed...PM me for details.

[jjjnettie (Jeanette)]

Sounds like you need another eye piece, or a barlow to give you the views you seek.

I ran into Jim, whom you bought the scope off, today at the post office.
He was saying how he hopes you enjoy it.

[Poita (Peter)]

Originally Posted by Merlin66

Peter,
Which eyepieces were you using?
I normally just use the ol' TV 10.4 plossl which gives great views.....
The spacer section can be removed...PM me for details.

I've tried a 5mm tmb planetary and a 10mm vixen and even the old 25mm kellner that came with the C8 and a WO 20mm, all could not reach focus.

That is good news if I can modify it for a bit more back focus.

[Poita (Peter)]

I've been loving it, but am concerned that his included warning was more a simple prediction of the future.

Originally Posted by jjjnettie

Sounds like you need another eye piece, or a barlow to give you the views you seek.

I ran into Jim, whom you bought the scope off, today at the post office.
He was saying how he hopes you enjoy it.

[Poita (Peter)]

To try and get more back focus, I attempted to modify the scope according to some advice from knowledgeable souls here (thanks Merlin66!).

DON'T MOD YOUR PST AT ALL IF YOU ARE NOT 100% SURE IT IS SAFE, YOU COULD SEND YOURSELF OR SOMEONE ELSE PERMANENTLY BLIND.

I thoroughly researched that the mod I was about to undertake was safe for my particular PST. Many are different, and this may not be safe to do on another PST.
In my case it involves removing the small extension tube before the eyepiece holder.

My particular model has the rear filter in the eyepiece holder and not in the extension tube, so it was perfectly safe to remove the empty extension, and replace the eyepiece holder to get more back focus.

I marked the position of the eyepiece holder in case the filter is aligned in some way (it probably isn't but I thought it couldn't hurt)

Sounded easy, I tried to unscrew it, but no go. I went out and purchased a 'Boa Constrictor' strap wrench
http://www.haron.com.au/images/strap_wrenches.png
as most guides say these will allow you to undo the extension tube.

Not. A. Chance.

It didn't even *think* about coming undone.
Eventually I held my breath, put two blocks of wood in the vice and the extension tube of the PST in between them and tightened the vice.
Still no go. Tried heating the joints. Nothing.

I ended up having to tighten the vice way past where I thought was safe (i.e. as tight as my wimpy arms would allow) before I could get the thing to unscrew. When it finally (2 hours of swearing later) came apart, I could see it was held in by red loctite, about a litre of it as far as I could tell.

Once the extension is removed it allows you to see inside to the prism and so forth inside the magic black box. I very carefully used my camera brush to remove any bits of loctite dust from the prism, and then carefully screwed just the eyepiece holder containing the filter back in.
It looks like the holder could potentially hit the prism, so I put a rubber o-ring in-between the PST body and the eyepiece holder to stop it screwing all the way in, just in case.

That is where tonight's story ends, I'll have to wait for the sun to come up tomorrow to check the results.

It really does feel odd to be impatient for the night to end so that I can use my scope!

Thanks again to everyone that gave me advice, and if anyone it ever thinking of doing any mod to a PST, remember, if you get it wrong, your's or someone else's eyesight could be lost, so if there is any doubt at all, just leave the thing alone.

Now to wait for sunrise...

[Poita (Peter)]

Well, after all that, it didn't solve my focus problem.
I decided to open up the side of the box and discovered the focus mechanism actually had an issue which was stopping it achieving full extension.
I fixed that up, and put the PST back to its stock standard configuration again.

Success! All eyepieces now work and achieve focus. The WO 20mm eyepiece is noticeably better than the included 20mm that came with the PST. The proms and surface details seem sharper.

[jjjnettie (Jeanette)]

woo hoo!

[Poita (Peter)]

Still had the problem of the tuning.

With the PST you turn a collar on the barrel to bring the proms and surface details into view, you then use the focuser on the back to make them sharp.

On my PST the proms only come into view when the collar is turned all the way clockwise (when standing at the eyepiece end), there just isn't quite enough travel in the collar.

Feeling brave after my previous adventure, I followed this guide:
http://home.freeuk.com/m.gavin/pstfixx.htm
It was pretty easy. I used the Boa Constrictor to remove the gold tube - (much easier to remove than the eyepiece holder!).
Then being careful not to touch the etalon thing, I rolled back the rubber grip, and screwed the whole assembly back together.
I undid the screw under the tamper seal, and removed it completely and slid the collar off.
Underneath are adjustment holes. I rotated the adjustment ring 5 holes clockwise (looking from eyepiece end) and put the collar back on, screwing it into the new hole.

Oh my God what a difference!
The proms come into view now at about the midpoint of adjustment rather than at the end. I can adjust them to be so much more visible, it is like a new, better telescope. I can't believe how much better it is.

I'll probably be spending the rest of the day observing!

Thanks to all the PST hackers out there, without your guides I would have been happy with quite a sub-par experience as I wouldn't have known any better. Now this thing really rocks!

[Merlin66 (Ken)]

Glad to hear that!
All's well that ends well.
Onwards and Upwards....

[Poita (Peter)]

Boy it's an ugly focus mechanism though.

Is there any magic filtering in the prism, or could it be replaced with a better focusing system and a better diagonal?

[graham.hobart (Graham stevens)]

Poita, I would be interested to know how you go with imaging with this beast
Regards
Graham

[Poita (Peter)]

Apparently for imaging you usually need to remove that extension tube, so my efforts in getting the loctite removed probably won't go to waste.

I've got to get the thing up onto the EQ6 yet! I do intend giving imaging a go though.

[Merlin66 (Ken)]

No, there's nothing in the penta-prism other than astigmatism ;-)
That's why the Stage II mod (dump the black box) is so popular.
The original 5mm blocking filter can be incorporated into a diagonal etc.
The focus is 200mm behind the etalon, so it's just a matter of suitable spacers...

[Poita (Peter)]

I get the feeling that is in my near future. I have a hunger for a sharper image.
Spent the morning perusing the sun, my favourite eyepiece so far is the Vixen 10mm LV, it gives the full disc, and lots of detail.

The TMB 5mm planetary has been good for a closer look at the proms, and gives about a 2/3 view of the sun.

You really do need to have a blanket over your head though to keep the side-glare out of your eyes.