Which eyepiece 10-20mm for 180 mak?

morls (Stephen) · #1 27-09-2018, 09:09 PM

Hi,

I want to get 3 eyepieces for my 180 Mak (f15). I've decided on two, but not the middle focal length...

1. Panoptic 35mm - 77.1 magnification, 2.3mm exit pupil, 0.82deg TFOV
2. ?????????
3. Delos 10mm - 270.0 magnification, 0.67 exit pupil, 0.27deg TFOV

The 35mm Pan gives close to the widest TFOV (although one day I might get a 55mm plossl, giving a 0.98deg TFOV), while I think the 10mm would get more use than anything shorter (suburban Melbourne most of the time).

I'm just wondering what others might suggest as a useful mid-range focal length to complete the set?

Cheers

Stephen

Wavytone · #2 28-09-2018, 08:51 AM

Stephen having had the same mak it has a real sweet spot around 13mm and if you have good seeing 8mm is useful on the planets.

Not sure you need 10 with those two.

morls (Stephen) · #3 28-09-2018, 03:29 PM

Thanks Nick.

The reason I'm thinking of 10mm is that I have an 8mm, and as yet the seeing hasn't been up to this amount of magnification. I'm happy to buy a few different short f/l for those exceptional nights, but spending the $$ on a Delos I want to get something useable most of the time.

It's interesting that you say 13mm is a sweet spot. There's 14mm and 12mm in the Delos range. Maybe a good range of exit pupil would be 2.3mm, 1.6mm (24mm Pan), 0.8mm (12mm Delos)

I had a 13mm Nagler once that was wonderful...

Wavytone · #4 28-09-2018, 07:01 PM

14mm would be good too. I found the 13 was optimal on nights with ordinary seeing. The seeing at my home is very ordinary but there are two sites I have access to that can turn on excellent seeing quite often due to their terrain and microclimate.

I'm using a Vixen SSW 14, 10 and 7mm and SLV 25, 12, 10, 9 with my current mak (f/13.5) and I also have 6, 5 and 4mm for "insane" power...

Don Pensack · #5 29-09-2018, 05:24 AM

Quote:

Originally Posted by morls

Hi,

I want to get 3 eyepieces for my 180 Mak (f15). I've decided on two, but not the middle focal length...

1. Panoptic 35mm - 77.1 magnification, 2.3mm exit pupil, 0.82deg TFOV
2. ?????????
3. Delos 10mm - 270.0 magnification, 0.67 exit pupil, 0.27deg TFOV

The 35mm Pan gives close to the widest TFOV (although one day I might get a 55mm plossl, giving a 0.98deg TFOV), while I think the 10mm would get more use than anything shorter (suburban Melbourne most of the time).

I'm just wondering what others might suggest as a useful mid-range focal length to complete the set?

Cheers

Stephen

180mm f/15 is a long focal length:2700mm.
The issue is in getting anything with a large exit pupil or a general use eyepiece with around a 2mm exit pupil.
If confined to just 3 eyepieces, they would have been a 55mm Plössl, a 30-32mm widefield and a 18-19mm widefield.
Your 10mm is a nice step up in terms of magnification, but a bit high for a "general use" high power, where a slightly lower magnification would be desirable.
Since you have the 10mm, and a 35mm, I'd first add something in the 18-20mm range, then think about that 55mm Plössl.
A low power of 49x and a true field of 0.98° and a 3.7mm exit pupil would be more appropriate as a low power, widest-field eyepiece.

If, on the other hand, you have other scopes and this is just your lunar/planetary/double star telescope, then a 17-18mm eyepiece would be useful as a "middle power".

In general, I usually recommend 4 eyepieces with a scope like that:
low power 4-10x/inch (28-70x) or 39-96mm focal length eyepieces
medium power 10-20x/inch (70-140x) or 19-39mm eyepieces
High power 20-30x/inch (140-210x) or 13-19mm eyepieces
Extra high power 30-40x/inch (210-280x) or 10-13mm eyepieces
Depending on which eyepieces you chose, you might get by with 3 eyepieces and a barlow lens.

morls (Stephen) · #6 29-09-2018, 09:08 PM

Quote:

Originally Posted by Don Pensack

Since you have the 10mm, and a 35mm, I'd first add something in the 18-20mm range, then think about that 55mm Plössl.

In general, I usually recommend 4 eyepieces with a scope like that:
low power 4-10x/inch (28-70x) or 39-96mm focal length eyepieces
medium power 10-20x/inch (70-140x) or 19-39mm eyepieces
High power 20-30x/inch (140-210x) or 13-19mm eyepieces
Extra high power 30-40x/inch (210-280x) or 10-13mm eyepieces
Depending on which eyepieces you chose, you might get by with 3 eyepieces and a barlow lens.

Thanks Don,

I don't have a 10mm yet, I was just thinking this might be a good option. Maybe you're right, and planning to get 4 main eyepieces is the way to go. I have the medium power covered with the 35 Pan, so a 55mm Plossl would be the low power. I've read good things about all in the Delos range, so am happy to aim for these in shorter f/l.

Maybe this as a set?
55mm Plossl
35mm Pan
17.3mm Delos
12mm Delos

Already have 35mm Pan, will get the Plossl last, so one of the Delos is next...

I already have a couple of not-too-bad 60 degree Dual ED eyepieces (15mm and 8mm), as well at the stock 28mm that came with the scope. I reckon these will keep me going while I save for the good glass.

Don Pensack · #7 29-09-2018, 11:54 PM

Now you're thinking.
A maximum field, low-power eyepiece is pretty much essential with a Mak.
It's hard to get a wide-enough field or a low-enough power with a Mak.
Not many scopes can use a 55mm Plössl.
You can also sometimes find inexpensive 55-56mm Plössls on the used market or even as new to try out the idea of that focal length.
The issue is that if the scope is used in light-polluted skies, the brighter image isn't necessarily desirable. In darker skies, though, it would make a nice complement to the 35mm.

doug mc · #8 30-09-2018, 09:06 AM

Mostly Luna and planetary scope hmmmmmm. A binoviewer.

Wavytone · #9 30-09-2018, 12:29 PM

Stephen the real limitation for low power on your mak is the field of view the scope can fill. Note the exit at the rear of the scope is significantly smaller than 50mm, this is what ultimately limits the illuminated field of view.

While these scopes have a 2” back I tried a few 2” eyepieces that have no field stop to see if it can fill the barrel edge to edge - notably a Vixen LVW 42, TMB Paragon 40mm and a Vixen LV50mm.

In the TMB 40 the illuminated field is totally vignetted for about the outer 10% meaning it can’t really fill the 2” barrel, and vignette was easily noticed within that. The LVW42 was similar.

The LV50 has a small field stop and was illuminated quite nicely and sharp edge to edge, giving a view of clusters like diamonds on black velvet, and I’d suggest one of these - if you can find one - as preferable over a Plössl.

Another bargain eyepiece that works nicely for low power is the 70 degree SWA 38mm, i currently use a Prostar one on my mak. You can find these under various brand names for under $100.

morls (Stephen) · #10 30-09-2018, 06:39 PM

Thanks for the replies,

A binoviewer would be pretty amazing, but I'm not ready to go that way (yet...). With the 35mm Pan I can get Omega Centauri framed very nicely, so I don't feel any real urgency to go wider at this point. I think I'll take my time and look out for a nice used plossl or LV50 (clusters of diamonds on black velvet is a great image).

morls (Stephen) · #11 09-10-2018, 10:14 AM

I saw your Matt, which has since disappeared...

The Baader Morpheus suggested looks good. I suppose the reason I'm staying with TV at this stage is that to me, they're a known quantity in terms of quality, and seem to hold value well. I know the price is up there, but if I take my time and save it can be (relatively) painless.

Probably also an element of not having the time/money to experiment much as well...

MattT · #12 09-10-2018, 03:27 PM

Deleted my post as I’m not sure one can compare a 6” f12 Refractor to an f15 7” Mak....or maybe you can?

Apart from the long ER on the Morpheus I also like the 2” usability. My fav Panoptic is the 22mm....what a beauty.

Before the Morpheus came along I did think that Delos 14 12 10 8 with a 2x Barlow to give 7 6 5 and 4mm would be great, but got side tracked, so I’ll never know but am very happy with the Morpheus set.

morls (Stephen) · #13 09-10-2018, 05:40 PM

Hi Matt,

Like you, I also like the 2" eyepieces. I've heard very good things about the 24 Panoptic in 180 Maks, so maybe the 22mm would be something else to consider...

Wavytone · #14 09-10-2018, 09:22 PM

Sigh... When I had the same scope as Stephen, 22 and 17mm were virtually unused. I used the LVW 42mm then went straight down to 13mm. If the seeing was really good, 8mm.

Even with my current mak its much the same - use a big 2" low power one first (SWA 38mm) then 14mm, even though I do have a 25mm.

Most of my eyepieces now cover the range 7-15mm as I am finding on the planets and double stars that just a 1mm difference can significantly optimise the details you can see clearly.