21mm Baader Hyperion + 14mm Fine Tuning Ring
21mm Baader Hyperion review (+ 14mm Fine Tuning Ring)
I've owned the 21mm Baader Hyperion about 3 times. I've only sold them to try other focal lengths close to the 21mm, (22mm Nagler Type 4, 20mm APM 100°, 20mm ES 68, 20mm Nagler Type 2, 23mm Axiom LX, 22mm Ultima LX, etc). The only caveat with the 21mm Baader Hyperion is EOFB, (edge of field brightening). Correction isn't bad in my telescope, (I own a 10 inch F/4.7 Orion Intelliscope), and although I did own a 2" GSO coma corrector, I no longer own one, so I use all of my eyepieces without one, and the 21mm Hyperion with thr 14mm fine tuning ring works really nicely without it.
I had an idea to try adding a 14mm Baader Fine Tuning Ring to see what would happen. Well, it not only eliminated pretty much all of the EOFB, but it also cleaned up the slight astigmatism I was seeing near the field stop from about the 70% mark down to about the 80% mark. Not to shabby since it is being used alone. In my telescope, the 21mm now gives me about 61x with a field of 66.8'. I currently own the newer type of the 21mm Hyperion which is shorter in length and it looks to be the full 68° as advertised. Eye placement is very easy and it plays better with filters in this configuration. In it's native configuration without the 14mm fine tuning ring, EOFB can be seen while using filters as well.
After adding the 14mm FTR, (fine tuning ring), I needed an additional bit of "in focus", so I used an old adapter from a 2" GSO barlow I had in my "astro parts" box and I added a small elastic band to parfocalize it with my other eyepieces. When I did that, I noticed that the 1.25" barrel was sticking out a bit, so I added an empty 2" filter cell I also had in my parts box, so that when I screwed on 2" filters, the 1.25" barrel would not "hit" the filter as I screwed it to the empty filter cell. When in this configuration, I also noticed that the field stop became somewhat "sharper" to my eye.
There is a bit of astigmatism still, but it is quite acceptable and not intrusive because it is now at about the 80% mark towards the field stop as noted. The Double Cluster looks really nice and so do other wide open clusters. I also wanted to mention that the current rubber eye cups that screw onto the Baader Morpheus eyepieces also screw perfectly onto the Baader Hyperion eyepieces. I used to own the 17mm Hyperion and that one in it's native form is very good. I would pass on the rest, except for the 5mm, which I also found acceptable.
I hope this will help some astronomers !!! I find the 21mm Baader Hyperion with the 14mm Baader fine tuning ring to be a really good configuration. It is still very good with glasses if you fold down the Morpheus eye cup and eye placement is very good and easy to hold the exit pupil. It also barlows well with a 2" GSO barlow with very minimal fuzzy edges. If you need a bit more eye relief, you can simply "unscrew" the rubber eye cup and get in a bit closer if your glasses are really thick.
Clear skies to all, and many thanks!
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