Quick Question - Blocking Filters

[PlaneSkies1]

Sorry if this topic has come up before...
I want to upgrade my Stage 2 PST mod BF5 - and just wanted to double-check whether there any problems, or difference in the viewed image if I upgrade to a Lunt BF1200 instead of a a Coronado BF10.
Thank you in advance.

[marktownley]

You should be fine, several people have done this. What ERF are you using with the scope?

[swisswalter]

Yes as Mark wrote, the B1200 works perfect on my mod

[Solarhound]

I am no expert on this but feel I should relate my own experience with this . I have built a couple of succesful PST stage 2 mods and purchased a straight through Lunt 2" B1800 blocking filter to use with them . This blocking filter would not work well at all with the Coronado etalon . It was impossible to get anything close to even lighting or bring up the contrast or detail , no matter what I tried the image was always blown out with a bright area . I also tried the b 1800 in my SM 60 II DS , i have a 2' Moonlight on this scope so I was able to try it in this one . The results were no different so the shop where I purchased the B1800 called Lunt to inquire . Lunt stated that their blocking filters will not work with Coronado scopes but that Coronado blocking filters will work in Lunt products . He did not say why , only that it wouldn't work . Lunt was very good about this and took the B 1800 back and refunded my money less 5% for restocking fee . So far my BF 15 has worked the best , I just wanted to pass on my experience with the B1800 on to you .

[PlaneSkies1]

Many thanks for the replies - very interesting!
I thought I'd read somewhere else that Lunt blocking filters will not work with Coronado scopes but that Coronado blocking filters will work in Lunt products, so definitely something for me to consider.
I was thinking of getting a 60mm Lunt scope with a BF1200 in the future (fairly distant future to be fair), so was planning to use the single diagonal for both Lunt and PST mod [110mm external baader D-ERF] scopes at that point, without having to buy a standalone separate blocking filter for the PST mod.
Looks like I will have to save up for the new scope a bit quicker than I anticipated so that I can make the test - and then decide whether or not an additional Coronado BF is needed.
Thanks again for your experiences

[Solarhound]

I believe that Lunt will sell their scopes without a blocking filter so an option could be to purchase a larger Coronado BF to use with your mod now and order the Lunt 60 without a BF , Lunt has already confirmed that the Coronado BF's will work with their products .
http://www.kwtelescope.com/telescopes/s ... ilter.html

[PlaneSkies1]

Thanks again!
If I can find a distributor in the UK that will supply a Lunt without a blocking filter, that would be a a definite option.
The problem in the UK that standalone blocking filters are very difficult to source and import (without excessive costs), and most vendors just supply complete stock packages (without many options). However, I will continue to scout around for the without blocking filter option as that would be absolutely ideal for me.
Cheers

[manu41]

You can find it in germany : http://www.teleskop-express.de/shop/ind ... tml/page/2

[DSobserver]

Colmic from thi sforum try many BF from coronado and Lunt for PSTmod II, and for him coronado BF15 was the best : lunt and BF30 too dark...

[marktownley]

Thanks again!
If I can find a distributor in the UK that will supply a Lunt without a blocking filter, that would be a a definite option.
The problem in the UK that standalone blocking filters are very difficult to source and import (without excessive costs), and most vendors just supply complete stock packages (without many options). However, I will continue to scout around for the without blocking filter option as that would be absolutely ideal for me.
Cheers

Just buy direct from Teleskop express in Germany...

[PlaneSkies1]

Thank for all the input and advice guys
This is getting complicated

[Valery]

This blocking filter would not work well at all with the Coronado etalon . It was impossible to get anything close to even lighting or bring up the contrast or detail , no matter what I tried the image was always blown out with a bright area . I also tried the b 1800 in my SM 60 II DS , i have a 2' Moonlight on this scope so I was able to try it in this one . The results were no different so the shop where I purchased the B1800 called Lunt to inquire . Lunt stated that their blocking filters will not work with Coronado scopes but that Coronado blocking filters will work in Lunt products . He did not say why , only that it wouldn't work . Lunt was very good about this and took the B 1800 back and refunded my money less 5% for restocking fee . So far my BF 15 has worked the best , I just wanted to pass on my experience with the B1800 on to you .

Two my B1200 (straight and diagonal) work with my SM40 (Coronado pre-Meade) just fine. Full of details. I think it is necessary to test prior of purchase.


Valery.

[Merlin66]

I agree with Valery, there are some very good examples of PST mods using the B1200 filters.
I'd like to understand better why the B1800 don't work as well........

[Allcart]

no problem getting a B1200 on its own in the UK. I just got one from http://www.iankingimaging.com/
He doesn't list them, but a simple phone call and tell him what you need will solve the problem. Not cheap though.

Incidentally, I use a B1200 with my pst mods and have not noticed any problem. I haven't compared it with a BF10 as I don't have access to one.

[Solarhound]

I was hesitant to post my experience with the B 1800 and do realize that many people have used the smaller Lunt BF's successfully . I came close to owning a very expensive paperweight and appreciate that Lunt took it back . The statement about Lunt blocking filter's not working with Coronado was Lunt's and not mine . If there were no previous issues I doubt that Lunt would have taken it back . The only other difference I see in my mod is that I use a Lunt ERF and most modders here use the Baader ERF , maybe that makes a difference .

[Merlin66]

The double filter BF arrangement (ITF followed by narrowband blocking) is independent of the ERF.
The bandwidth and central wavelength of the ITF needs to match the final blocking filter..it could be the slight variations in design/ central wavelengths give the problem....