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Old 15-04-2021, 09:26 AM
Tropo-Bob (Bob)
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StarGuider Dual ED EPs

I received my new set of 6 EPs from ProAstroz this morning. Cost was $415 + postage.

They are approximately the same size and weight. I was delighted to find that the 4 longer focal lengths are exactly parfocal when tested with my 81mm ED Vixen. The 8mm needed an extra 1 or 2milimetres of outfocusing, whereas the 5mm needed 2 or 3 millimetres of infocusing.

I was also very pleased to find that these 4 parfocal EPs where also parfocal with my Vixen 30mm Plossl. This means that they will also be nearly parfocal with the Vixen NPL plossls, Tak & Fujiyama orthoscopics and some unbranded silver plossls that I already own.

It’s too early to say how good they will be stargazing, but I will advise re this within my capabilities (so not overly technical). I will also report more on their ergonomic comfort etc.

I must also add that they arrived very well packed and as expected, in mint condition.

In the second image, they are arranged according to size with the smallest EP in front and the tallest at the back.
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Old 16-04-2021, 10:40 AM
Tropo-Bob (Bob)
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I was able to trial these last night on doubles, clusters, nebulae and the New Moon. I again used my 81mm F8.7 Vixen.

I thought the most sticking feature of these EPs was the lack of either Pincushion or Barrel Distortion. I could not detect any in the 15 & 18mm EPs, very little pincushion distortion in the 5 & 8 mms and a noticeable, but still small amount in the 12 & 25mms. I was able to sweep without any noticeable affects even with the 25mm EP. In this regard, it is much better than my 24mm Panoptic. This lack of distortion will also be helpful for terrestrial viewing. No more bent poles and lines!

Nor did the EPs suffer from field curvature. The 81mm scope only has a focal length of 625mm, so curvature was a possible issue. (As many are aware, curvature is greatest in smaller focal lengths and does not relate at all to the F ratio of the lens.)

The EPs showed details well on all objects, but the 5mm was hampered by the seeing conditions. I overcome this by barlowing the 12mm, so effectively obtaining a 6mm option, which I found more useful to split doubles. The EP/ Barlow (Celestron 2x shorty) combination came to focus only a 2 or 3 mms inside the EPs normal focal point.

The EPs performed well when viewing the Gem Cluster in Carina. The colours seemed particularly bright and striking.

In the daylight, I thought the larger 4 lengths were all parfocal. However, when viewing stars, I had to make very minor adjustments each time that I changed EPs.

The EPs did show some off-axis astigmatism but it was tolerable.

Another positive are the twist cups on the top of the Eps (as shown in the attached image). Together with the rubberised exterior, the Eps feel ergonomically easy to handle. Furthermore, as these are light Eps, there is no danger of my little refractor becoming unbalanced when they are being changed.

Edited: I meant to say that there was slight pincushion distortion, not barrel distortion.
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Old 01-05-2021, 02:37 PM
Saturnine (Jeff)
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An interesting appraisal of the Dual ED eyepieces. I have a pair of 25mm that I use for wider field bino viewing. They do work quite well in the F8 and F9.4 refractors but do suffer from coma in the F6 newts, not unusable, as the outer 33% of the field is affected and can be ignored a lot of the time when concentrating on the central area of the FOV.
The shorter focal would be worth a look from what you say. Thanks for the write up.
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Old 09-05-2021, 09:20 AM
Tropo-Bob (Bob)
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After using these EPs for 3 weeks, the 15mm is emerging as my favourite.

I also own a 15mm DeLite which I find to be noticeably better when observing the Moon.

Last night, I used my 140mm SS Vixen last night to find some faint objects in Lupus and Norma using a 15mm DeLite. At the end of the season, I changed over to the 15mm StarGuider. There was not a huge difference. Yes, the view was not quite as good at the edge, but it was still very engaging.

Overall: The 25mm is proving to be a great navigation EP and excellent for sweeping. However, the view is a little bit below par once I stop sweeping.

18mm: I really like this EP almost as much as the 15mm. However, it is a bit close to the 15mm in magnification so often is bypassed.

15mm:

12mm: Another very good EP, which I also like to use with a 2x barlow when more magnification is require.

8mm: Its ok, but I would rather reach for one of my Tak or Fuju orthos, which are nearly parfocal with the previous four EPs. (the 8mm & 5mm are not parfocal)

5mm: Much the same as with the 8mm, except that I find it a bit fiddley with eye placement compared to the rest of the range. I can not see myself using it very often.

My observing seasons often start slow, but if conditions are good, then I become more serious about using my good gear. I can see my seasons now starting with these 25 & 15mm EPs and going from there.
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