Lyra etc.etc

[dobsonian]

:)Hello,
Having just aquired a nice shiny new 40mm eyepiece, I was keen to see how it performed. Last night ( Monday ) was reasonably clear, but the transparency was so so, LM was 4.5. I got out the 250mm dob and plopped in the 40mm eyepiece and soon located M2 in Aquarius. This globular is inferior to M13, but a nice sight nevertheless. I was struck by the richness of the stellar background, the faint stars everywhere. Next stop Lyra. The famous M57 was soon found, but in the 40mm it looked like a faint star out of focus. I have read about it being described as spectacular, but I my opinion it is nothing of the sort.Anyway, I replaced the 40mm with a 7mm Nag, and the Ring nebula really showed up nicely, like a smoke ring, but I could not see the central star as it is around mag 15.The bacground was glorious, with faint coloured stars everywhere, and numerous faint doubles.I noticed that most stars do not display diffraction spikes around the stellar discs , and this I think is due to the fact that I made the flat mirror supports as thin as possible, along with a flat mirror slightly undersize at 55mm. All in all a pleasant two hours observing, but at midnight the ever present clouds became total, and I went to bed.

[Administrator]

Hi dob,

I have a 250mm newt too and the 40mm is my fav eyepiece! I have a pentax XL 40mm and a meade 3000 40mm, both are great eyepieces. Even though the meade only has a 40deg FOV its sharp from edge to edge, unlike the pentax which suffers a bit because of the newt's f4.8 speed. Would love to have a go on one of those Naglers some time, I've got the 7mm pentax XW and its 70 odd degrees.

Anyway, any beginners reading this, you don't need expensive eyepieces, a decent plossl will show you just as much and will prob be sharper than most wide angles!

[dobsonian]

Hello Robert,
If we ever get this observing group up and running, then we can compare eyepieces. Over the years I have accumulated a number of eyepieces, some good, some bad, and some useless. During the last apparition of Saturn I used my 130mm APO refractor a lot. this scope is F8 and places a lot of demands on eyepieces.For sheer sharpness and contrast ( very important ) I would vote for a 10mm Clave plossil. This frog made ocular has a field of only 50 degrees or so, but that does not matter for planetary observing.The field is sharp to the edge and absolutely no false colour at 250x using a 2x barlow.To go off at a tangent, which I often do, I discovered that the Lidl eyepieces supplied with the famous refractor work very well with my homemade 100mm achromatic F13 refractor. My choice of 3 eyepieces from my collection would be for 250mm F5 dob is 40mm Meade 4000, 10mmClave and 7mm Nag X31, x125, and X180, but eyepieces to astronomers are like shoes or handbags to women, you can't have too many.
Regards,
John.

[Administrator]

Hi dob,

That would be good, especially since there seems to be a lot of members out there hoarding some serious equipment!

I've heard of those claves, would love to get my hands on one, the 50 degree field wouldn't bother me as my eye can only really handle 40-50 degrees at a time anyway. Any more is just an expensive luxury. What makes viewing pleasurable for me is sharpness not FOV, although if you have an APO refractor and a nagler then I wouldn't complain!

Hey you didn't mention what the 40mm was, is that the Meade 4000?

[dobsonian]

Hello Robert,
Yes the 40mm is a Meade 4000 type, not cheap, but not too expensive. I had a cheap Kellner, but as you know these are afflicted with the problem that every speck of dust on the field lens shows up as large gob in the field of view. The Meade is a true Plossil, with all the virtues that the design has. The new Meade 5000 types don't seem to be anything other than a repackaging exercise, as it is becoming more and more difficult to improve on current designs.
That said one of the best views I have had of Jupiter was with the 130mm refractor and a 10mm Orthoscopic by Celestron. This eyepiece is about 20 years old, and at that time the plossil was starting to supersceed the Orthoscopic.
This 10mm eyepiece also showed me 5 satellites of Saturn, but to be honest I suspected one might have been a faint star. This eyepiece gave a dark field with the minimum of light scatter around the image. This is usually achieved by blackening all surfaces inside the eyepiece with matt black paint, needless to say not on the lenses!!

[Administrator]

Hi Dob, wouldn't mind comparing the 3000 with the 4000. unlike the rest of the 3000 line, the 40mm was made in Japan and cost a lot more!