I have been thinking of buying a Baader Herschel Prism for many years now, as this has been described as the best herschel prism available. My main interest with this would be for solar imaging, although it would be very good for solar viewing as well. Unfortunately the cost has always been fairly high, and it just never made it up the priority list.
As the price on Amazon seems very reasonable, I decided to buy the Visual version, as it is the less costly of the two, currently £297.37 on Amazon.co.uk, which is even cheaper than in many other countries. Just be aware that the description on the Amazon website is not accurate – you need to look at the item model number (the 2956500P photographic version costs £371.57 currently). My thinking was that I would try the Visual version first, and add on further neutral density filters as the need arises.
It is important to know that there are two different versions of the Baader Herschel Prism – the visual (V) version which comes with the 2″ Baader Solar continuum filter (RRP £98) and one Neutral density 3.0 filter (RRP £39) , and a photographic (P) version which comes with these two filters and 3 further neutral density filters (0.6, 0.9 & 1.8).
I have only managed to use this once so far, as I have been working the whole week. Hence I will do more posts on this in due course. The things I would particularly like to do comparison tests for are:
1) comparison of images with Herschel prism vs Baader Solar film
2) Baader Solar continuum filter with and without Baader UV/IR cut.
3) One Baader Solar continuum vs double-stacked filters (as I have two 2″ Baader Solar continuum filters now)
4) UV solar imaging (Baader U) with the Herschel prism ( to see how close to Calcium K-line the images would look)
Here are the initial images taken with the Baader Herschel prism the day it arrived.
Equipment used: Olympus E-PL5, Skywatcher ED80 refractor, Celestron 1.25″ Ultima 2x APO barlow, Baader solar continuum & Baader ND 3.0 filters.
Camera settings: ISO 1600, 1/1000 secs. Images processed in Capture One Pro 7 and converted to B+W.
The impression I get is that there is more detail visible in the sunspots as well as the solar granulation in the images captured, but I will do some comparison images in future posts.
What I have noted with the Baader Herschel prism:
1) For imaging, you will likely need to remove the 2″ click-lock to allow the camera to be closer to the Herschel prism; I found that without my Celestron Ultima 2x barlow, I was not able to achieve focus with my Skywatcher ED80 when the click-lock was in place.
2) The filters can be removed and interchanged with different ones – so the only difference between the two versions (P vs V) is simply the number of filters it comes with.
3) The ceramic solar finder screen does feel slightly warm to touch but not excessively hot – but still best to be careful.
4) I was not able to white balance fully with the Baader Solar continuum and ND 3.0 filter – likely due to the presence of infrared (I will need to try with the Baader UV/IR cut filter to see if it makes a difference, or use an unmodified camera).
I do like the Baader Herschel prism, as it does capture a good amount of detail from the sun. With the predicted increase in solar activity which is predicted to peak during 2015-16, now is probably the best time to get such items to learn how to get the most out of them. I am sure the images I get will be even better once I have had more time to use it.
Equipment: Olympus E-PL5, Skywatcher ED80, Baader Herschel prism, Baader Solar continuum filter, Baader ND 3.0 filter.