First light PST-B120

michaeloconnell wrote: Anthony,

I think that is more of a generic note re ERFs rather than specific to the Daystar one.
AFAIK, the Daystar ERF has evolved over the years and a couple of different flavours are available.
Is yours red or yellow?

Michael,

I have the RED filter. In fact, I got a reply back from Jen and she made the obvious comment about the colour of the filter indicating the passthrough. Since mine is red, Jen mentioned that everything below 600 nm gets cut-off whereas it is 500 nm for the yellow filter.

To this end, the UV is not an issue whereas the IR may be. Now, is there enough IR to raise a warning flag?

Jen also mentioned to me that they require f30 so as to have parallel beams of light entering a system. She does not know what will happen with the f10 PST etalon and where there will be incident rays at the blue end and which should (she believes) raise the passthrough at the h-alpha line (ie. above 0.7 A).

Anthony.

daveg wrote: Anthony, Sebastien's images are great but I think I would be agreeing with Michael here about risking something as good as an FSQ

Dave,

I have a Bresser 102/Achr EMC refractor (102mm diameter, 900mm focal length) I picked up about a year ago as a potential piggy-back guide scope. Being at f9, it nicely matches my AP160 which is at f9.3 when stepped down with the Daystar 130mm ERF. As a result, I have my guinea pig for when I am all set for initial testing to see what transpires and to what extent things work out.

If things do work out, I will then risk things with my FSQ since it costs much less and is certainly much more easily available than my AP160. If things work out well with the FSQ, I will have to sit down and think really hard about moving the testing onto the AP160.

Alternatively, I can pursue the SkyWatcher route described at the start of the thread.

Anthony.

Trevor,

Thanks for the info in your reply above as well as the private email.

Anthony.

The PST etalon comes with a lens on each side of it. The incoming light from the f/10 objective to converted to parallel (or near parallel) rays via the first lens directly in front if the etalon. The rays pass through the etalon and are then re-converted to an f/10 beam by the lens on the rear of the PST etalon.

Etalons, irrespective of who they are made by, work on the basis of parallel rays of light. This is why front mounted filters work best. In terms of rear mounted filters, Daystar have found that f/30 is close enough to parallel for it to work well.

The PST mod requires 200mm of back focus from the lens at the rear of the etalon.

Of the scopes you have, the achro would be my choice to try it first.
I doubt the system will come to focus in the AP160.

An interesting read:
jp-brahic.chez-alice.fr/page%20perso.htm
(use google to translate from french)

and his latest results:
www.cloudynights.com/ubbthreads/showflat...d/sb/5/o/all/fpart/1
I think they speak for themselves.
He must also live in an area of very good seeing and have a very good PST etalon.

Note that he is using a PST etalon with a Lunt BF and Baader D-ERF.
Surprising because others more knowledge than I say they are not compatible and Lunt also say they aren't.
Interesting....

Michael,

Check out these results from Germany using a modified PST at f18: www.cuwohler.de/hasun/has11-2/20110421-0605.html ... seeing is believing!

Anthony.