Peter Drew

10x50 Bresser, 10x50 Opticron Elite, 10x80 German ww2, 25x102 self built, 50x150 self built, 50x300 (reflecting) self built.

There is no need to "sacrifice" a PST to convert it to a larger set up. If you cut off the "gold" tube a few inches in front of the tuning ring the back half becomes a Ha eyepiece. With a suitable sleeve, the front half can be rejoined to reconvert it to standard. I use this method to either fit to a range of larger refractors or provide a grab and go unit to determine whether there is sufficient activity to warrant setting up something better. You still have to have a suitable ERF for the upgrade.

Visited Opticstar in Hale, Greater Manchester with a colleague on Monday.

Well stocked showroom, friendly, helpfull and knowledgeable staff. Well worth a look, specially if it's your nearest outlet.

No way! .

Although town centre viewing is not ideal for DSO's, a 10" will be much better than a 3" and there is a range of filters available that will improve the situation. Light pollution has far less affect on lunar and planetary performance, in some instances it can be beneficial as it reduces glare. The biggest difference you will find, however, is the increased physical size and weight of the 10". Photos are usually not very representative of what can be seen visually, specially DSO's.

Much as I should have known better, I twigged only recently, that as Ken says, a donor telescope faster than F10 may well have the objective vignetted by the 20mm etalon aperture of the PST. Based on this, I now calculate that the 80mm ERF on my Sky 90 mod is providing a clear aperture of only around 53mm which belies the outstanding performance it gives. I do know someone who has a 90mm and 60mm coronado and claims that on average days the 60mm is preferable to the 90 so this might be a factor.

I managed to obtain a 145mm diameter ERF so I can "stretch" my PST to that aperture. Although it is true that the bandwidth of the etalon remains as standard, the extra scope aperture pays dividends in respect of resolution during good seeing and will stand higher magnification. At the end of the day it depends on what type of image you prefer, my preference is for the bright prominence performance from a .7 etalon as opposed to the darker disc performance of a double stacked unit. I'm happy with the enhanced PST type performance as a result of the "mod".

A deal breaker for me would be whether the Lunt could be modded in the same way as the PST can be, leading to much better performance at reasonable cost than either of the original configurations.

Many thanks for the info which confirmed my suspicion, am now waiting for a clear day to attempt the fix. BTW I have also noticed that the solar image in this example is yellowish-orange whereas my own pst's are a reasonably deep red, all have the blue coating. Any comment?

Is it possible for the user to reset the etalon tuning ring, I have an early pst in which the position of the tuning ring is at the end of its travel before the prominences and surface details start to appear.