Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_dslr_mirrorlesss_winners.thumb.jpg.9deb4a8db27e7485a7bb99d98667c94e.jpg

GlassWalker

PST mod revival (again)

Recommended Posts

I think I first thought about doing a mod late 2012, and... suffice to say I've got distracted and done nothing about it last year. So this year, I will finally get round to the mod!

To recap, I have two PSTs, one I'm keeping stock, one I'm modifying. I had all sorts of wacky ideas, but have now decided to go the tradition route and have ordered a TAL 100RS. The only other major component I need then is the D-ERF. I remember it was a common trick to get an under-sized one and insert it into the tube part way down. Here's where I'm getting confused. My previous notes suggest it was a 75mm one, but now I can only see a 70mm one on sale. Next one up is 90mm and also comes with a hefty price lift. Was it actually 75mm or is my memory failing me? I don't think I have much choice other than go for the 70mm.

Edited by GlassWalker

Share this post


Link to post
Share on other sites

I'd prefer to order from UK.

I have compared the part number between the UK 70mm ones and the 75mm on Baader's web page, and it is the same. Just different measurement method?

Edit: then again, the one from TS works out cheaper... :)

Edited by GlassWalker

Share this post


Link to post
Share on other sites

No customs fees due from Germany as we're one happy euro family, for now. Postage is reasonable, which may mean "slow". Then again it has taken me over a year to get this far...

Share this post


Link to post
Share on other sites

Hi get the Baader one, it is very, very good.

As said there are no charges buying from another EEC country.

gallery_4564_1903_35414.jpg

My PST conversion and the man (Peter Drew) who did it.

gallery_4564_1903_9305.jpg

And here is the holder and cover plate.

The slot is cut centeredat 15.5" from the front of the lens holder.

The tube is cut to 26.5" also from the front of the lens holder.

I removed all the baffles from the tube and flocked it.

Share this post


Link to post
Share on other sites

The 75mm is the size of the filter unmounted, this will be nearer 70mm clear aperture when it is. 70mm is more than large enough for a 100mm objective and represents a considerable saving financially over a full aperture front mounted filter.  :smiley:

Share this post


Link to post
Share on other sites

Thanks all, I'll put the order in once the coffee has kicked in, perhaps lunch time :) I was only looking at the Baader, but my confusion was that UK sites seem to list it as 70mm, whereas older notes and Baader themselves call it 75mm.

Any other useful accessories I should consider that might come in handy? Like something to hold the filter?

Share this post


Link to post
Share on other sites

Filter ordered. Postage was a bit more than I thought earlier, but I guess as I wasn't signed in that was probably german postage, not to UK. Sill going to be cheaper anyway.

I'm having search fail looking for a filter holder of some kind though...

Share this post


Link to post
Share on other sites

Thanks, will order that in the morning. The D-ERF has shipped and due Friday! It might overtake the scope in that case as I'm not expecting that until Monday.

Share this post


Link to post
Share on other sites

Scope arrived today, although it is still in its box. D-ERF is still on target to arrive tomorrow. I wont be working on the scope at weekend anyway since tools are at work!

Anyone used the Thorlab holder before? Debating if the spanner wrench is required since it is double the price of the holder, or could I bodge it with other random bits as a one off job? I assume there's a screw in ring that holds the filter in place? I'm also wondering if the spanner wrench may be handy for other uses in future, but chances are it'll be so rare it isn't worth it.

Share this post


Link to post
Share on other sites

I used one for my PST mod with internal ERF. With regards to the spanner - don't bother. It is easily possible to tighten the ring by hand. You certainly do want it to be too tight incase you set up stresses on the glass if it warms up at all. When I say warm, I mean only slightly as anything would if sat out in the sun for any length of time, which hopefully it will be if you are viewing / imaging the sun -;)

Ian

Sent from ma fone using Tapatalk

Share this post


Link to post
Share on other sites

Good luck with the mod. I may be in a minority here, but I was disappointed by my Stage 1 PST / TAL mod, primarily because of the apparent cropping of the field of view you get using the tiny 5mm BF filter in the PST eyepiece holder.

In fact, I prefer to now just use my reassembled unmodded PST, leaving my expensive front-end 110mm D-ERF and TAL unused. However, a smaller than expected tax bill this year means I'm considering ordering a 10mm BF to get a wider view and make the whole expense a bit more worthwhile!

Share this post


Link to post
Share on other sites

I know the BF will be a limit factor also, but since I have two PST I got a stock one for the wider image, and can use the mod to pick off interesting details. A bigger BF would make sense, apart from the high cost I seem to recall they demand.

Share this post


Link to post
Share on other sites

For others reaeding this, it's possible to use a combination of two photographic filters as a cheaper alternative to the Baader ERF.

Really interested to hear how this turns out. In a fit of too-many-telecopes-buy-more I am the proud owner of a Stellarvue 80 achro, which has been cut short for solar PST work. So I've got the OTA and the "ERF" substitute, but no PST yet :/

Please keep us up to date, and photos!!

Share this post


Link to post
Share on other sites

That sounds wrong and dangerous to me ... !!!! 

More details please , I would say that the filters you refer to are totally inadequate for the purpose you suggest ...  :mad:

Share this post


Link to post
Share on other sites

That sounds wrong and dangerous to me ... !!!! 

More details please , I would say that the filters you refer to are totally inadequate for the purpose you suggest ...  :mad:

Come on CJ , wakey , wakey .... still waiting for theses filter specifications ......  :cool:

Hi Steve

Yes, to anyone considering solar astronomy, I would urge the utmost caution. Be absolutely sure about what you're doing. Especially if looking with your eyes rather than a camera, as infra-red light will permanently damage your eyes without you feeling pain.

I must be clear: I know very little about solar astronomy. I am merely referring to information I had seen elsewhere on alternatives for Energy Rejection Filters. Here is some info on using 2 photo filters instead of a Baader ERF to filter out IR:

http://solarchat.natca.net/index.php/en/this-is-solar-chat/12-solar-scope-modifications/96974-pst-mod-complete

And posts #31 onwards here:

http://stargazerslounge.com/topic/108905-my-70mm-stage-2-pst-mod/page-2

Noe that post #32 suggests photographic filters' optical quality not being good enough. However, Dennis Put in the Netherlands (an accomplished solar photographer) tells me he used them successfully (and he's taken some amazing photos):

"For the ERF I used the photographic filters as can be seen in the pictures that I sent. If you look at the filter transmission curve Baader promises for its Baader D-ERF filters, then one can conclude that the combination of the two photographic filters that I used will very much approach the desired passband in red light, blocking IR and UV and only passing a red band of light. My experience and that of the previous owner are that the etalon and other internal parts do not suffer from thermal heating. A friend of my has measured the transmission of a Baader D-ERF 110mm by himself with professional equipment, and the outcome was that there were distinct transmission peaks in both UV and IR, the areas of light most harmful to the human eye (especially far IR). It is not said that his method of measuring is the best and optimized for such equipment as these filters, but the transmission peaks do not arise from nothing. Now, with a modified PST you will have a ITF filter behind the blockingfilter (an IR blocking filter), but to further optimize I used a 2" 12nm H-alpha filter as mentioned earlier. Nevertheless the Baader D-ERF are good filters for imaging purposes and I have made good results with them."

Clear skies

John

Share this post


Link to post
Share on other sites

If, as I believe, the Stellarvue 80 achromat is F5 then it won't be a suitable donor telescope for a PST mod which requires a minimum of F10 to retain the full aperture of the objective. A 80mm F5 objective would be vignetted to 40mm aperture by the 20mm PST etalon.   :smiley: 

Share this post


Link to post
Share on other sites

If, as I believe, the Stellarvue 80 achromat is F5 then it won't be a suitable donor telescope for a PST mod which requires a minimum of F10 to retain the full aperture of the objective. A 80mm F5 objective would be vignetted to 40mm aperture by the 20mm PST etalon. :smiley:

Hi Peter

This one is an old Stellarvue 80/9D, f/9.4, so it will work ok. The guy I got it from, Dennis Put is a real enthusiast. Just in December, he won the first Patrick Moore Prize from the BAA, but was too modest to mention to me why he'd come over to London in December (to receive the award, I guess!). :)

What do you think of the use of photographic filters for the ERF?

Sent from my iPhone using Tapatalk

Share this post


Link to post
Share on other sites

IMHO photographic filters are no good as an ERF. Optical quality and stability being the main concerns. They are designed for photography not precision astronomical work.

I think you'll find that the resonance peaks for the D-ERF are so low that the attenuation is still well within safe limits.

A combination which includes a BelOpik UV-IR/Kg3 gives absolute maximum protection.

Share this post


Link to post
Share on other sites

Back to the original topic (my feeble attempts at PST modding), to recap I have the TAL 100RS although yet to be unpacked. Also received the 75mm D-ERF which is a depressingly small piece of glass for the cost. I know it's high precision and all that, but still... then again, per area, I'm sure other astronomical filters I have cost even more. The outstanding item is the filter holder, which is ordered and hopefully arriving some time next week.

Sky looks surprisingly clear at moment. If I can find the solar film I made up previously I might test out the TAL in white light and get some practice in I haven't done any solar in a long time.

The photographic filters, interesting but personally the only reason I might look at them is if they bring much bigger sizes down to a reasonable cost. In a quick look at the general filter curves, you get increased losses from having more glass, plus I hate to imagine working out any stray reflections!

Oh, any tips on BF upgrading? In practice, how much of an upgrade would the Coronado BF10 be? I'm more imaging than visual, so I hope that would help significantly in field of view and light falloff. Now, does anywhere in Europe sell it at a reasonable cost? By reasonable, put it this way, it is $500 in the US. Importing it is one option, even with customs fees. I'd pay a bit more to get it more locally as long as it is sane.

Share this post


Link to post
Share on other sites

Good to hear that the objective was F9.4 and as such should be a good donor. I share the views expressed by Merlin66 on the filter issues. For Ha observation the priorities are safety, performance and cost in that order. The larger blocking filters are nice for visual and almost obligatory for imaging due to the small field of the basic 5mm blocking filter.  :smiley:

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By astrorg
      Hello
      I have been away from this forum from possibly July - I never find a lot of time to do anything these days, same to be able to relax reading and interacting Astronomy forums.
      I asked here a few ideas about making a solar scope or modifying whatever I had and I was recommended to also see Solar Chat Forums and I did.
      Thanks to solarchatforums I have been able to do something decent and here is what I have done so far - very slowly!
      1. I purchased a second hand PST and replaced its ITF with Maier one from the US and it finally had a clear image coming through + moved Etalon screw to third position - all the usual thing everybody does [after I researched it]!
      2. used a new SCT screw-on short focuser [used once or twice on a LX200 R Classic] and using Teflon tape I screwed the PST Etalon to the focuser and purchased a 2" adaptor to fit on Etalon.
      3. then used a Chinese 2" to 1.25 and modified the 2" side socket taking internal ring off and making 3x 120° threaded holes and 3x nylon thumb screws and used that as an adaptor to fit the original PST eyepiece holder - strangely enough at present this adaptor is also used as a tilter ... until I buy a proper camera tilter
      4. then fit the above eyepiece holder into the SCT focuser with 2" to 1.252 adaptor in it and screwed the whole Gold PST tube with Etalon in it and made a BETTER PST - see image

      5. I also initially tried a 2.2x DSLR camera Lens magnifier in front of PST and it decently works too - so PST will be fine for full solar disk mainly and without the 0.5 angstrom - not forcibly needed, I am probably around 0.7 as it is!
      6. more importantly, I decided to make my own 90mm solar scope using the above bits and pieces.
      7. with the help of Solar Chat Forums [great guys with a lot of knowledge, some are professional - i.e. they know the optics mathematical details - which helps] I purchased a cheap Bresser AR90/900
      8. the ONLY usable thing there ... is the main tube, a nice and thick tube - the rest is ALL plastic!!!
      I dismounted all parts and saw tube shorter ... a bit too much ! - I could have saved ~6cm really as I went with original ideas, but forgot I was using a different telescope from my initial thoughts - silly me!
      So, I added a 6cm extension - no problems there to reach the 20cm inward needed for the PST Etalon which has ~20cm FL
      9. initially I used a Tuna Fish 100g tin to adapt the SCT focuser onto my AR152 and fit Etalon inside the focuser to get near the 20cm needed- lets call it Quark unit - which it is really!
      It worked well, so I decided to add a second focuser to tune the Etalon ... getting back to AR90/900 ...
      10. I was trying to avoid overspending, I could not afford to spend too much - then I remembered I had a unused AR102SX which in my mind I guessed ... the focuser should over AR90/900 and it did!
      It just fits perfectly - then drilled three holes for the holding screws et-voila'
      11. I purchased a second hand 75mn Baader D-ERF and fit it INSIDE the AR90 tube at about 20cm inside from the front air-spaced doublet lenses, as there are the usual internal rings soldered in and just sit on it and I have about 70mm aperture  - i.e 70mm width from the D-ERF for photons to get through.
      At that ~20cm distance from front lenses the beam is still very large - probably about 60-65mm - there is no heat in between - no need for air-escaping holes
      12. when I have the time I will make a solar finder scope and fit it on the tube - not that is really needed - I usually use CDC to get there almost over The Sun [having an almost exact spot on the yard!] - then use my eye without eyepiece and look thourgh the PST eyepiece holder for solar shinging and centre the telescope over The Sun.
      Well, it works well after tuning Etalon focuser correctly and then focusing/tuning Etalon etc. - the usual.
      See some images - still learning imaging/processing and a lot more to learn about Solar ... a lot!
      I will probably need to get a Power-mate 2.5x when I can afford it!
       
       

      1st mod - without the original black box - it works so much better - better focusing and sharper viewing too.


      This is the AR90/900 shorten tube with AR102SX focuser and adaptors to test it normally
       

       
      This is complete with the Quark Unit on the right side
      Since this image there have been some changing - do not use the revelation adaptor any more and added a 6cm 2" extension.
       
      Here are some images:

       
       
       

       
       
    • By Richard Shaw
      I acquired a second hand Coronado PST. The focus knob doesn't seem to have any effect on the image and, although it turns, it feels as if something inside the scope is "slipping".
      Is it worth opening up and taking a look to see the focus knob in action?
      Is there anywhere that services the PST without sending it outside the UK?
      Are there any nasty surprises if I open it up (springs, pressure points etc)?
    • By SacRiker
      I recently acquired a PST and had my first light today...it took a bit of work but I was able to see some great stuff through the EP. However, when I tried to hook up my smartphone to the scope with a phone adaptor I was completely unsuccessful in capturing any good photos. Everything looked way out of focus and I couldn't come close to seeing any of the prominences on the phone that I saw visually. Is this due to the PST's setup? Or am I doing something wrong? I was attempting to do it with an 8mm EP. 
    • By lnlarxg
      Hope this is the right place to ask about the Coronado PST
      i recently acquired this scope and I can’t get any surface details to show on the sun, I have played with the tuning ring but apart from being able to see some flares on the rim of the sun, no surface details came through. I was using my own 8mm and 11mm Explore 
      what I saw was just a red blob, pretty much like white light viewing with a red filter. Turning the tuning ring only changed the intensity of the light coming through
      is this what is expected of the PST? Or do you think I am doing something wrong or my PST may well be faulty?
       
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.