Jump to content

Banner.jpg.39bf5bb2e6bf87794d3e2a4b88f26f1b.jpg

PST Filters Equiv


Recommended Posts

Hi Guys

Can someone explain to me why you cant buy filters that allow you view the sun the same way you can with a PST. I had a chance at 6PH to have a go at one and of course instantly screamed "I want one" but £600 is a lot of money for a scope you can only look at one object. In truth i'd pay it but i don't understand why there aren't filters you could buy for either end of the scope that would do the same job.

Can someone explain my lack of knowledge to me please

Link to comment
Share on other sites

You can buy them and set it up on a refractor but a PST is generally a cheaper option.

Check the thousand oaks site out it has loads of info and filters.

http://www.thousandoaksoptical.com/halpha.html

I should add that you must have every part in place though and I'm not certain just what filters and erf's you would need.

Edited by JB80
Link to comment
Share on other sites

I'm by no means an expert but I did ask myself this question the other year. Evidently it's all to do with 'etalons' which are fitted in the scope. These are far more selective than filters which are a bit of a blunt instrument when you also need to filter out 99.99% of the suns power.

Link to comment
Share on other sites

The PST is still good value at £600+ when you consider that 20 years ago you would need a second mortgage to see the details that it now can show. As for looking at just one object, but  what an object! a real star to actually observe its ever changing dynamic activity. It would probably be best mounted separately from the Mak. Did I mention that solar viewing is warmer with no lack of sleep?   :smiley:  

Link to comment
Share on other sites

The PST is still good value at £600+ when you consider that 20 years ago you would need a second mortgage to see the details that it now can show. As for looking at just one object, but  what an object! a real star to actually observe its ever changing dynamic activity. It would probably be best mounted separately from the Mak. Did I mention that solar viewing is warmer with no lack of sleep?   :smiley:  

Hey I'm not belittling the object :grin:

The Solar filters i have are great for letting you look at the spots etc but there's nothing better then the emissions/eruptions

Consider that added to the list i guess

Link to comment
Share on other sites

The PST (and similar scopes) actually show you an incredibly narrow range of frequencies.  From memory (so this may be wrong), the passband of a PST is about one angstrom wide centred on the Ha emission frequency.  Ten angstrom is 1um.  I can't remember what the published price is for the 3um Ha filter that Olly P bought earlier this year, but when you compare the prices of 3um and 7um filters with a PST that achieves a one angstrom passband, it makes the price of a PST look quite fair.

James

Link to comment
Share on other sites

:eek: :eek: :eek: :eek: :eek: :eek:

£600 it is then

Lol that is why I opted for a PST :)

You can do stage one and stage two mods to a pst that allows you to use the etalon and the blocking filter in a larger refractor. You need to buy an energy rejection filter for the front though that comes in at around £400 for a 90mm. Oh and obviously the cost of a donor scope. I have an Evostar 102mm that is f/10 (same as the pst) when money allows the plan is to do a stage one modification.

Something else for you to think about :p google it and you will find a lot of information about it :)

Link to comment
Share on other sites

Hi Alan,

Viewing our closest star is amazing. It is the most dynamic object we have to observe / image. It is constantly changing - you do not see galaxies and nebs change before your eyes!

When observing Hydrogen alpha you are looking at a wavelength of 656.28 nm. There is a lot of precision in manufacturing two pieces of glass to create an etalon that enables you to isolate a very narrow bandwidth of light.

I was lucky enough to purchase a PST 2nd hand. It was inexpensive because the coatings on the primary had started to degrade - the dreaded "rust". I was not particularly bothered as I only wanted the etalon for a PST stage 2 modification. This meant that with a few other bits I was able to cobble together a 4" solar scope for about £1000. yes that sounds a lot but if I was to purchase a 4" solar scope off the shelve it would be in the region of £5000 :shocked:

You can purchase filter to add to a standard refractor as shown here:- http://www.solarscope.co.uk/sf-range.html

To see what modifications people have done have a look at solarchat:- http://solarchat.natca.net/index.php/en/this-is-solar-chat/12-solar-scope-modifications

As Peter has already said, there is nothing like sitting in the warm and not missing out on sleep when observing / imaging. Admittedly it is more difficult at this time of year because the sun is not always observable because of how low it remains during the winter.

To quote my wife - "I think its good that you have got into solar observing" "why" I asked. "Because you don't have to worry about clouds" :huh:

Let me tell you, if you get annoyed by it being cloudy at night, thereby stopping you observing galaxies and the like, its no different during the day when you to observe the sun. It can still be cloudy :grin:

Ian

Link to comment
Share on other sites

My PST mod came in under 1000 euros all up, I was lucky to get the donor scope and ERF second hand from Ken(Merlin666) and the PST was purchased when they were cheaper.

It's well worth the upgrade too.

Link to comment
Share on other sites

Jarrod,

I'm Glad you enjoy the mmoded PST!

Yes, Ha solar filters are very expensive, but nothing like they were years ago!!

The heart of the system is a very specialised Fabry-Perot etalon filter...this is made from highly polished (1/100 wave!), highly reflective, thick glass plates held together at very close tolerances (0.19mm)....nothing like the "normal" multi-coated glass filters used for night time observing....

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.