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Back in the Saddle with an XLT 150

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#1 Sarkikos

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Posted 13 September 2013 - 07:55 AM

I finally took out a telescope last Friday, 9-6-13, after three months of recuperating from back and hip injuries. Not my usual 10" Dob, but the XLT 150 on a Voyager II alt-az mount. I didn't want to take a chance on a relapse.

Transparency was good and seeing about 8/10 at the dark site.

Gamma Delphini - In my 6", I saw this as yellow-orange and green.

Epsilon Lyrae - The Double Double split cleanly for my 6" at 94x (8mm setting on my Baader Zoom) and a bit less than that. Not the prettiest split I've seen of the four stars, but a definite dark line between each pair.

I didn't check any other doubles, not even Albireo. For this night I showed the Messiers and other bright DSO - mostly from memory - to my family. We viewed galaxies M31, M32 and M110 in Andromeda, M33 in Triangulum, M51 and companion in UMa, M74 in Aquarius; open clusters M52 in Cas, M39 and M29 in Cygnus, M34 in Perseus, the Pleiades and the Double Cluster; the long string of M objects in Sagittarius/Scutum up to M11; globs M13, M15, M2, M22, M28, M4, M30, M56 and M71; asterism M73 in Aquarius; planetaries M57, M27 and M76.

We also looked at the Veil in Cygnus, using a 2" Lumicon O-III filter with my ES 100 20mm, and later my ES 82 30mm. Both gave nice views of all three major parts of the Veil. The 30mm yielded a somewhat larger TFOV at 3.3 degrees, compared to 2.7 degrees for the 20mm. But with the Paracorr II, these TFOVs were reduced to 2.8 and 2.3 degrees respectively. I wasn't quite able to fit the entire Veil in the FOV of the ES 82 30 with Paracorr. All three major parts of the Veil looked bright and obvious through both eyepieces.

My family and I - as well as a group of girlscouts and an observing buddy - caught the launch of the lunar probe. I swung the XLT 150 over to it and was able to follow its progress pretty easily at about 30x at the lower setting of my Baader Zoom. The body of the probe looked as if it were boiling with the heat of friction, and it left a long thick tail behind. I pointed the scope ahead of the probe so my daughter could see it as it sped through the FOV.

A star test on Polaris showed that this 6" f/5 Dob has a somewhat different diffraction pattern when comparing infocus and outfocus at 5 waves, not so much at 10. Maybe 1/5 wave lower order spherical aberration when comparing my memory of the diffraction pattern to examples I've seen online. Unfortunately I didn't have Suiter's Star Testing with me. But so far my C6 SCT seems to have a better star test than the XLT 150, with no difference infocus/outfocus seen at 5 waves with the C6.

I need to do a more thorough star test of the XLT 150 on my porch at home, viewing Polaris, with my copy of Star Testing at my side. I don't like to spend much time testing equipment when I'm at a dark site.

Maybe next New Moon I'll take the 10" Dob.

Mike

#2 RAKing

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Posted 13 September 2013 - 08:44 AM

I'm glad to hear you are back outside and doing better. I had back surgery over Labor Day last year and I am still recovering 12+ months later. It can take a while.

Just take it slow and easy! :waytogo:

Ron

#3 Sarkikos

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Posted 13 September 2013 - 09:19 AM

Thanks for the support and kind words. I'm lucky that the back and hip problems only involved muscles, not vertebrae or disks. The back is completely healed. The hip is giving me only aches now and then, not the severe sciatic pain I had at first. Good luck and good health to you!

I do plan on taking the 10" Dob out to the side of my house this Saturday night, just to check out some new equipment. The Moon makes a good test object.

:grin:
Mike

#4 Eric63

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Posted 13 September 2013 - 05:29 PM

Glad to see you back in the game Mike.

I have the SW 150F5 version and I also found the diffraction pattern less similar on either side of focus, but this scope still gives amazing views! In fact it's a touch better than 127 Mak on planets, go figure. Flocking also helps quite a bit.

Looking forward to more reports, but do take it slowly with your back.

Eric

#5 BoldAxis1967

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Posted 13 September 2013 - 06:58 PM

Wow, you sure did take in a lot in one night.

A year after purchasing my XLT 150 with the CG-4 I am still impressed with this scope. It really shines on open clusters. It is such a joy to use, small, light weight and surprisingly effective. A good performer as they say around here (i.e. CN). Also, an excellent choice when still testing the waters after back surgery.

LB

#6 Sarkikos

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Posted 14 September 2013 - 07:57 AM

Glad to see you back in the game Mike.

I have the SW 150F5 version and I also found the diffraction pattern less similar on either side of focus, but this scope still gives amazing views! In fact it's a touch better than 127 Mak on planets, go figure. Flocking also helps quite a bit.


I intended the XLT 150 to be mostly for rich field low power at my dark site, which is what I mostly used it for during this observing session. It gave good images of all the objects I listed in my report. :ubetcha:

My best small scopes for planet/lunar are probably the C6 SCT or my 6" Bosma Rumak. But the Rumak is so heavy and takes so long to cool down I hardly ever take it out. The optics on the C6 are so good I do expect it to trounce the XLT 150 for planet/lunar, and maybe even the 6" Rumak.

In any case, Saturn had set before I could get a look at it with the XLT, and I didn't want to wait for Jupiter. I did see both Uranus and Neptune that night, but no surface features were visible - didn't expect to see any! Though I could tell they were discrete disks and not stars, especially Uranus.

Mike

#7 Eric63

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Posted 14 September 2013 - 04:35 PM

I've read a few times that a C6 is often better than a 6"F5 Newt on planets and I wonder if its the mirror quality that makes the difference. The Newt has a smaller CO (33%) compared to 38% in the C6, yet many say that the C6 is better. Is it because the F5 mirror is difficult to make in mass produced scopes and the C6 is not? Is it because you introduce a barlow in the newt or perhaps that it's difficult to get perfect collimation in the F5? :shrug: I'm just curious how other 150XLT owners find their scope on planets. I'm asking because I find that this size makes a nice all around portable scope for low power wide field and planetary. Not great, but darn good enough.

Eric

#8 azure1961p

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Posted 14 September 2013 - 10:17 PM

I wonder if its a coma issue with the reflector. I've seen sct planetary images of similar aperture fast newts that looked better despite the larger CO of the sct.

Pete

#9 Starman81

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Posted 14 September 2013 - 11:10 PM

Nice to see you got back in it and with the XLT 150. That's an impressive array of objects observed without GoTo!

I used this scope while observing through sucker holes a couple days ago... I used it with a ParaCorr (Type 1 Tunable top) but was unable to reach focus with it + 22T4 or 13 Ethos. Seems like you had no issues, but then again you are using a different ParaCorr (don't know how much of a difference that makes). I use my GSO 2x ED barlow tube without the barlow as my extension tube to reach focus with this scope and using that with the ParaCorr + eyepiece, there wasn't enough out-focus and using it without, there wasn't enough in-focus. So I guess I need a different, smaller extension tube.

#10 Sarkikos

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Posted 15 September 2013 - 08:08 AM

Eric,

I've read a few times that a C6 is often better than a 6"F5 Newt on planets and I wonder if its the mirror quality that makes the difference.


Bingo!

The Newt has a smaller CO (33%) compared to 38% in the C6, yet many say that the C6 is better.


I don't think 5% will make a significant difference when both CO's are already well above the 25% rule-of-thumb for CO%. Quality of the optics is more important here.

Is it because the F5 mirror is difficult to make in mass produced scopes and the C6 is not?


Not sure. But one is a paraboloid and the other is a sphere.

Is it because you introduce a barlow in the newt or perhaps that it's difficult to get perfect collimation in the F5?


I've never used a Barlow with the XLT 150. I hardly ever use a Barlow/OCA with any of my telescopes, except to reach focus with a binoviewer or filter wheel.

It is easy to reach virtually perfect collimation (perfection is never possible) with an F5 Newt. A Cheshire/sight-tube, autocollimator, experience and a little patience is all you need. I know a number of people who never had a Newt - or put off getting one - because they were afraid of collimation. Pffft! It is to laugh. Nothing to it. :grin:

:shrug: I'm just curious how other 150XLT owners find their scope on planets. I'm asking because I find that this size makes a nice all around portable scope for low power wide field and planetary. Not great, but darn good enough.


I haven't viewed any planets with the XLT 150 except Uranus and Neptune. I did manage to discern that they had disks, which is about all you should really expect in a 6" Newt, unless the optics are superb and the seeing is excellent. But if Jupiter, Mars or Saturn had been well positioned (I didn't get there until Saturn was at the horizon) I would have checked out the XLT's optics on those.

But judging by what I see from the diffraction pattern on my XLT 150 vs my C6, I think the C6 will be the better planet scope. My XLT should be fine for lunar, since there are so many levels of detail on the Moon's surface.

But I'm talking about my XLT. Yours might have a better star test.

Mike

#11 Sarkikos

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Posted 15 September 2013 - 08:21 AM

Pete,

I wonder if its a coma issue with the reflector. I've seen sct planetary images of similar aperture fast newts that looked better despite the larger CO of the sct.


The degree of coma should be the same for all f/5 Newts. At least this is my understanding. I've seen very finely detailed images of planets with my 10" f/4.8 Newt. Of course that's a 10" vs a 6". And my 10" has good optics.

I really think that it is a question of the optics here. A 6" SCT with a better star test than a 6" Newt will generally show better images of planets. But don't sell the XLT short yet. I've yet to view bright planets with it. (Uranus and Neptune don't count.) The proof is in the pudding.

On the other hand, I never thought of a 6" f/5 Newt - even with fine optics - as a planet scope. A decent Moon scope or a great rich field telescope, yes, but not really a planet killer. A 6" f/8 would probably be a better bet for planets because of its smaller CO%. I think my C6 would still be better than the 6" f/8, unless the Newt had very good optics. Even so, I'd rather use a larger aperture Newt - 10" to 14" - for planet work.

Mike

#12 Sarkikos

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Posted 15 September 2013 - 08:36 AM

I do have another 6" f/5 mirror that I've stored away. It was for a telescope I was working on but never finished. I'm not much of an ATMer. My excuse is that I don't have the tools or the space for such work here in a condo. Any slouch with a basement full of tools would have a better go at it.

My notes for that mirror say "objects were sharp across the field. Saturn showed nearly edge-on rings, sharp disk edge, couple faint bands at 188X in TMB 4 under mediocre seeing." I might swap that mirror with the one that's in the XLT 150, and see which has the better star test.

Mike

#13 Sarkikos

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Posted 15 September 2013 - 08:44 AM

LB,

Wow, you sure did take in a lot in one night.


But you know there was one glaring omission ... I didn't look at the North America Nebula! That would have been nice in the XLT 150. :ubetcha:

Mike

#14 Eric63

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Posted 15 September 2013 - 09:01 AM

Thanks for the reply Mike.

Your answers make a lot of sense and it's what I pretty well suspected. I can collimate my Newt beautifully and as a result I get some sharp planetary detail (for this instrument). Now my 127Mak has a much better star test, yet I find that the Newt just lightly edges it out, but I think that this has something to do with the brighter image on the 150mm newt compared to the Mak that is only working at 120mm. They both show the Cassini division as being very sharp but neither scope will show more detail in the rings. On the globe, the Mak shows two very distinct bands of shading (one yellowish and one light brown) and the Newt shows three bands. I did test the Newt in excellent seeing once (the only time I experienced this) and I was able to get a very sharp image at 280X, but the detail was the same as at 180X.

I realize that this is not a planetary scope, but I have to admit that I was quite surprised at how well it did. Since planets are becoming my favourite targets, I suspect that a third scope will join my lineup in the future. :grin:

Eric






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