I am getting a 28" f/3.3 made by Peter Read, SDM . I have several Naglers including a Nagler 7. I want something stronger for planetary viewing when conditions warrant. Which is the better option? I'd appreciate your feedback
Thanks
Stephen
Pukemaru Observatory
Northland
NEW ZEALAND
Hi Stephen. With that Dob you will have to run a Paracorr, so a 3.5mm eyepiece is going to give you 770x. That is not a very practical magnification to use. I would say you are better off spending money on a longer focal length. Maybe start off with the 7mm and see how that performs with your sky conditions.
For a given focal length the Delos will be sharper than the Nagler, yet an Abbe Ortho will be better again than the Delos as a dedicated planetary eyepiece. For the ultimate in planetary observing, nothing beats a bino viewer, in my opinion. Best alround eyepiece I have ever used for both DSO and planetary and lunar is the Delos.
At that magnification with the sorts of objects you will be viewing, and with tracking, I expect that having a slightly larger field of view (Nagler) will be less important that comfortable eye relief. The Delos has 20mm eye relief compared with only 12mm for the Nagler. If you wear glasses the Delos will be far more comfortable to use in particular. I have a few Naglers with 12mm eye relief, and I don't mind it, but it is at the tighter end of the scale for that aspect of eyepiece use. If it were me, I would get the Delos.
I doubt you will get to use that level of magnification very often. People make all sorts of claims about how much magnification you can get for every extra inch of aperture, but at a certain point things seem to plateau out.
Phil Townsend from our forum has a 28 inch f/3.3. I doubts he would have an eyepiece anything as high powered as that in his kit!
I have a 3.5 Nagler and don't wear glasses. It works fine for me, but the eye relief certainly feels less than the 12mm. If I was in the market for a 3.5 today and not prioritising portablility the way I am, it would be going for the Delos. Can't comment much on the power a 3.5 will give in the dob concerned, but it seems so high that you might have tpo wait years for the right conditions.
I can't help much as I only have ethos and panoptics but I do have a 3-6mm nagler zoom. In my NP127 refractor, I am rarely able to use 3mm (which is only 220x) due to the seeing where I am. On exceptional nights - 3 in 10 years - I've been able to use 440x which is not bad for a 5in scope. So as others have said, even though your 28" should be able to handle very high mags you would be limited by the seeing. I use my 3-6mm nagler exclusively for moon and planets and it is great but the eye relief is terrible! I've heard great things about the delos and the extra eye relief would be advantageous over the naglers in my opinion.
I have a 28" f4.2 Webster, I use mostly Ethos or an occasional Nagler with a Paracorr. I've never tried a Delos I might have to get one and give it a go. I use the high power Ethos (3.7 and 4.7) very occasionally when the seeing is good.
I find Servocat tracking makes a big difference when viewing planets at high power.
Thanks, everyone for your help.
I already have a 7mm Nagler (and 9/13/20/31). I think I will try the 7 out and if seeing permits, I might go to the 3.5 Delos. But if seeing isn't very good with the 7mm, I won't buy the Delos.
Alan, the mirror is being made by Mike Lockwood, USA
I really appreciate your support.
Merry Christmas and I hope you are all getting more clear skies than we are in norther New Zealand. Two fine nights in the past month!!!!!
Someone mentioned a paraccor. Peter is going to fit a SIPS (Starlight Integrated Paracorr System for Coma Correction).
If you are not familiar with these, I quote from Starlight Instruments (and i have no affiliation to this company): "Starlight Instruments in conjunction with TeleVue is proud to introduce the last word in coma correction for Dobsonian telescopes. We call it the Starlight Integrated Paracorr System or SIPS for short, referred hereafter as SIPS. SIPS is unique in that it integrates the first class optics of the TeleVue Paracorr - Type 2 Coma Corrector with our state of the art, finely crafted FTF2015BCR focuser." http://starlightinstruments.com/stor...&product_id=50
That will be a great telescope. I have the SIPS on my Dob and think it is a wonderful piece of gear. You know you really should try a Delos with such a nice telescope, but a longer focal length that will see a lot of use.
Sorry to be late to the comment party. It sounds like your chosen name for the scope is accurate...it indeed sounds Glorious!
I think your plan to try your 7 mm Nagler before buying another eyepiece is a good one. In my opinion with tracking taken care of, the ergonomics of the Delos line (or Pentax XW) may be of interest.
IF you have not used longer eye relief eyepieces before, they do take some getting used to in terms of placing your eye but once done a properly adjusted they are a joy to use.
I think the quality will be quite similar, I have Naglers, Ethoi and Pentax...see how your seven goes and then as a next step consider a 5 mm Pentax...
28" f/3.3 = 2347mm focal length.
With SIPS: 2699mm focal length.
Call it 2700mm.
25X/inch of aperture is 700X. This might be occasionally useful in good seeing in a 28". I have a friend who has used up to 1050X with his 28" and it did OK. But 700X is, though not usable all the time, not really the top magnification possible with a 28".
That's a 3.9mm focal length.
So if I were to suggest a planetary eyepiece that MIGHT get used a little more often, and which could double as a great eyepiece for planetary nebulae, globulars, and small galaxies, it might be a 4.5mm Delos.
Magnification: 600X. Only 21.4X/inch of aperture, so a reasonable high power that won't push the optics too far. And fairly practical in a 28" scope.
As for using a Delos as a planetary eyepiece, why not? It has good control of scattered light, it has pretty close to the world's best wavefront accuracy for a widefield, and it has no detectable tint. And it can double as a superb DSO eyepiece.
Someone who buys a 28" f/3.3 isn't looking for a planetary instrument anyway. It's a superb DSO scope that also can be used for planets and Moon and double stars.
And if, wonder of wonders, seeing is perfect, the 4.5mm can be put in a Barlow.................
