Active Region - 23rd May 2010

Two images from of the active region:

H-alpha @ 8:30am



CaK @ 1:15pm



Michael.

Michael, my respects!

Do you also have a modified PST?

Anthony.

Anthony,
I don't use a modded PST.
I use a Daystar 0.6A T-Scanner with a 135mm D-ERF on my TEC140.
After much work researching the pros and cons of the PST mod, I feel this route is a bit safer on the eye.

Michael.

Obviously well researched Michael. The results speak for themselves. Well done .

Thanks John.

The PST Mod is a good idea and offers a very low-cost method of entering high-resolution h-alpha imaging. From a cost perspective, if you want a 90mm h-alpha setup:
90m D-ERF = 365euro (assuming you make your own adapter to connect it to front of telescope)
PST = 600euro
Adapter = 50euro
COST = 1015euro
Compare this to the Coronado and Lunt 90mm options which are many multiples of the price and you can see why people may be tempted to try the PST mod. Dave Gradwell is certainly getting very good value from this configuration.

It has a few downsides however:
1. Variability in bandpass of PST. Some are 1.0A, others are closer to 0.7A.
2. Optics of PST around etalon were not really designed around high resolution imaging and so image quality may vary due to precise configuration and alignment of optical elements.
3. There are different versions of the PST which Coronado released over the years and as a result there are questions marks over which version is safe to use for visual observing when modded. No problem though for imaging that I am aware of.
4. Blocking filter in PST is 5mm - acts as a restriction in the setup. To get around this, you need to spend a further several hundred euro on a Lunt 12mm blocking filter + adapters to hook it up to the PST etalon.

I got a 135mm D-ERF which matches my TEC140 nicely. I bought a secondhand Daystar 0.6A filter and then only needed a 4x powermate. All in, I payed only a little more than an equivalent modded PST+Lunt filter configuration. However, I have the reassurance of a system designed for visual use. Also, the Daystar filter holds it's value for trade-ins - Daystar has a very good policy in this respect: www.daystarfilters.com/UpgradeMe.shtml

Michael.

Hi Michael

Just to advise that there are NO known questions over safety of PST mods. Tests have been done using both IR and UV meters and none have shown any leakage to the eyepiece of any harmful radiation.

DG