barlow/telextender/power mate advice and zoom lens

[DAT]

Thanks! All valid points. I found the extender at 20% off so have gone with that. I am gifting the 150 p to my dad (750 focal length) and was going to simplify things for him by giving him the zoom. It will be interesting to see how the telextender works with that, if not, will consider one high mag es 52 ler option for planets, the 5mm works well for me but varies according to conditions, the telextender also fills gaps when paired with my low mag eps. I will test out and reply on this thread, thanks again!

out of interest , I often travel to Girona as my wife is from there, do you know of any particularly good places to observe?  ( because of luggage I probably will takes binoculars) someone has recommended an observatory but it is all the way over on the west side of Cataluña

5 hours ago, Chandra said:

The TX 3x with your 24mm eyepiece would give you around 94x or 125x (depending on whether it is the 150P or 200P reflector), while your 5mm eyepiece gives you 150x and 200x respectively, these are not very similar magnifications and exit pupils. On the other hand, it must be considered that Telextenders sometimes cause intrafocus problems, especially with equipment with a short focus path as is the case with Newtonian reflectors. If you feel that your current 5mm is not providing you with enough quality views, I still think that the most suitable option would be the zoom, as long as you can have one to compare it with your astigmatism, and, if not, I think that I would opt for one or two eyepieces with a low focal length and high Er, such as those from TS Optics (HR Planetary or N-ED), Omegon Cronus WA, Explore Scientific LER 52º and others.

 

[bosun21]

19 minutes ago, DAT said:

Thanks! All valid points. I found the extender at 20% off so have gone with that. I am gifting the 150 p to my dad (750 focal length) and was going to simplify things for him by giving him the zoom. It will be interesting to see how the telextender works with that, if not, will consider one high mag es 52 ler option for planets, the 5mm works well for me but varies according to conditions, the telextender also fills gaps when paired with my low mag eps. I will test out and reply on this thread, thanks again!

out of interest , I often travel to Girona as my wife is from there, do you know of any particularly good places to observe?  ( because of luggage I probably will takes binoculars) someone has recommended an observatory but it is all the way over on the west side of Cataluña

 

The TX worked just fine in my 8” and 12” reflectors.

[Second Time Around]

On 23/11/2023 at 18:35, Ricochet said:

Given this, which eyepieces do you currently own? In my opinion zoom eyepieces work best when you need that fine granularity for high power observing, but are not so useful at low and mid powers where you don't need anything closer than root 2 changes in focal length. 

 

Ricochet makes a very good point about zooms being most useful at high powers and I'm in full agreement.  Having said that, there are sometimes objects where a small change in focal length even at low powers can make a small but significant difference.  This is with deep sky objects that have a low surface brightness.  They may be bright in total, but if that's spread over a large area the surface brightness will be low.  It can also occasionally happen with the fainter areas of some more normal objects, and in a few extreme cases there have been reports of a faint object with a low surface brightness being invisible altogether but then becoming visible with a small change in focal length.  In this case such an object may be invisible in a fixed focal length eyepiece but visible in a zoom.

Edited December 4, 2023 by Second Time Around

[Louis D]

On 25/11/2023 at 04:22, Chandra said:

On the other hand, it must be considered that Telextenders sometimes cause intrafocus problems, especially with equipment with a short focus path as is the case with Newtonian reflectors.

Interesting, I've found just the opposite.  My old, long focus Barlows won't come to focus in refractors when used in the diagonal because they require so much in focus (up to 4 inches).  Of course, you can use them ahead of the diagonal at a higher than marked power without focus issues.  This in-focus issue doesn't arise in all but the smallest Newts because the secondary mirror is so far away from the focuser.  You simply insert the Barlow 4 inches into focuser.  Try doing that with a diagonal!  Of course, you may introduce a diffraction effect if the Barlow protrudes into Newt's light path.  In practice, I've not noticed it with even my longest Barlows.

Shorty Barlows come to focus in everything in my experience, so are generally the better choice unless going for the highest quality views possible.  I've found that the older, Japanese made long Barlows of the 90s produce the tightest images at high powers.  The difference is subtle, but it is there over shorty and mid-length Barlows of similar cost (sub $150).  I've not tried any of the super premium Barlows or Powermates because I can't justify the cost involved for how little I use Barlows.

[Chandra]

On 11/25/2023 at 4:35 PM, DAT said:

I often travel to Girona as my wife is from there, do you know of any particularly good places to observe?  ( because of luggage I probably will takes binoculars) someone has recommended an observatory but it is all the way over on the west side of Cataluña

Beautiful lands in Girona... however, to the north it is easy to find wind (tramuntana), and the coast is not the best place to observe due to the mist and breeze. The best place would be inland, the Guilleries area, north of Montseny, although it will be very difficult to obtain a sky with better Bortle than class 4. I also wouldn't be able to tell you a precise and valid place in that area. In fact, I don't even think that in the Girona Pyrenees it is easy to get dark skies. I remember many years ago (more than 30) that I had gone to the Vallter 2000 area and the sky was dark, but now I don't know what it will be like. As you have been told, the best skies in Catalunya are towards Lleida, in the Pre-Pyrenees, where there are several areas accredited with the Starlight seal (in the areas of Noguera and Pallars Jussà). In fact, as you know, the Montsec Astronomical Park (PAM) is located there.