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Why a Questar 7

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#1 JimP

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Posted 23 February 2021 - 09:37 AM

I have been thinking about the purchase of a Q7. In the past I have heard from dealers that it takes forever to cool down and only performs about as well as a 5” apo. I would want one for many reasons, not the least of which is how beautiful both the Q3.5 and Q7 are but specifically for double stars. If you have or have had a Q7 can you tell me about your experiences? I would especially like to hear from double star observers but, would like to hear from anyone with any experience. Pro or Con.

 

best,

 

Jim Phillips 



#2 Optics Patent

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Posted 23 February 2021 - 11:01 AM

Of dozens of Questars I own (nine mounted) it is literally the only one I have used since having it suitably mounted, except for one Hawaii vacation accompanied by a PG1 in a Pelican.  I live under bright skies, so mostly lunar and planetary.  Never once even peeked though the excellent competing brands.

 

But "suitably mounted" is the issue.  It's heavy when mated to the base, and challenging ("ding bang ow!") every time for mating and demating.  I never used it until it was on a rolling tripod that lets me roll out and back in 2-3 minutes each way.  The classic mount is beautiful and for me emotionally essential.  But it's not economical  because of a need for a mount and pier/tripod on which to mount the mount.  And frankly, scaling up perfection introduces imperfection.  It's a less graceful reach to the RA knob, for instance.  The diagonal prism control is rather heavy to move a prism with 8x the mass, and cares whether it's looking at the eastern horizon of west, affecting whether the prism is rising or descending.  But it's heaven and I wouldn't change it.  A practical observer would put the Q7 barrel on a fine GEM.

 

Optically, where the 3.5 is perfection, the Seven is a leap beyond due to the physics.  In summer, I've never seen much concern for "warm-up" and in mild cool weather it's enough to put out the scope on a shady porch before sunset.  (I have seen variation among examples for cool down sensitivity - it may be how evenly the mirror contacts the spindle - defocused images show a mirror with a "steaming" sector - I should post a video).

 

Emotionally for me, Questar is the ultimate telescope, and the Seven is the ultimate Questar.


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#3 Mike Allen

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Posted 23 February 2021 - 11:56 AM

I have a Q7 Astro that is used extensively for double stars.  On a steady night it reaches beyond the Dawes limit into the Sparrow range.  Star colors are pleasantly vivid.  As with the Q 3.5, or any obstructed telescope, the first diffraction ring of of a focused star is brighter than that seen in an unobstructed instrument.  I rarely see a second ring, but when I do, it is usually very dim.
 

Comparisons between the Q7 and a 5-inch apo refractor are curious.  Although I have never looked through a 5-inch apo, physics and my experience tells me that a 7-inch telescope will produce a brighter image than a 5-inch.  Perhaps there is  slight difference in contrast, but a difference in resolution may not be as significant in every case.  A significant difference is the maximum true field of about one degree for the Q7.   At any rate, the compact design of the 7 allows for a more comfortable viewing experience than a longer tube refractor.  Just my opinion though.

 

The time required for the instrument to adjust to outside air temperature is certainly more than a refractor.  I have mentioned in a previous post that I keep my instrument in its padded travel case, which is stored in a room that is not heated.  I usually set up the scope about about sunset, which gives it ample time to adjust by the time I’m ready to observe.

 

I have no regrets about purchasing the Q7, just as I have had none with my Q 3.5.  The instrument is well built, and provides a wonderful and very comfortable observing experience.  Questar Corp. and Jim R. has provided excellent support.  
 

Observing reports with my Q7 are posted elsewhere in this forum.


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#4 JimP

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Posted 23 February 2021 - 12:43 PM

The one I am looking at is Pyrex without broadband coatings. The latter is OK as Questar does not recommend BB coating if living near the sea. I live 5-6 months out of the year on a barrier island. 
how do I figure out the year from the number in the middle of the serial number. P7-xxx -DP?

 

best,

 

Jim



#5 Optics Patent

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Posted 23 February 2021 - 04:31 PM

The one I am looking at is Pyrex without broadband coatings. The latter is OK as Questar does not recommend BB coating if living near the sea. I live 5-6 months out of the year on a barrier island. 
how do I figure out the year from the number in the middle of the serial number. P7-xxx -DP?

 

best,

 

Jim

No secret date code.  Questar maybe can tell you.  Samples (first three are/were my own as reported by Questar, second is as reported by a seller in 2019):

 

1970: #90

1981: #484

1992: #736

2007: #955



#6 LorenBall

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Posted 24 February 2021 - 12:36 PM

Because I currently own a 3.5" 50th Anniversary Questar, it is the most natural thing in the world to wonder about the performance of a 7" Questar.

I bought this Meade 7" f/15 Maksutov Cassegrain telescope ​in the 1990's, and because it works so well, I have always had a hard time pulling the trigger on a 7" Questar.

Pragmatist that I am, getting 95% of the performance of the 7" Questar at 5% of the cost, seems to be OK with me.   smile.gif

Earlier today in a different thread, I posted 4 images of asteroids taken with this telescope and my iPhone XR.

I seriously doubt that if I had taken the same images with a 7" Questar, anyone would notice a difference in side by side images.

Of course, the 7" Questar is a much finer telescope in every way. No one is likely to dispute that.

 

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#7 Codbear

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Posted 24 February 2021 - 08:08 PM

I wonder if these dealers who have stated that a Questar 7 performed about the level of a 5" apo actually did side-by-side tests.

 

Between 2017-2020 I performed side-by-side comparisons  between the following:

 

1986 Questar 7 (BB) and Astro-Physics 130GT

Questar Astro 7 (Quartz) and TEC180 apo

Questar Astro 7 and Televue NP127 apo

 

Predictably, all three apo refractors destroyed the Q7 and Astro 7 on wide-field views. With the NP127, AP130GT and TEC180 putting up maximum views of over 4, 3 and 2 degrees respectively, The Q7 could manage around .8 degree FOV, while the Astro 7 with a 41mm Panoptic came in at a little over a degree FOV.

 

However, for planetary, lunar and DSOs it was not even close to a contest against the 5" apo's. A properly acclimated Questar 7 should and does put up more detailed views of the Moon without having to "reach" for the magnification, given the native f13 or so focal length, unlike the apo's which needed barlows to attain higher magnification. The contrast on the 7s was amazing, showing more complex filamental structure of M42 than the 5s. While globular clusters were resolved deeper in the 7s, I do like the wider framing of the globs that the 5" apo's provided.

 

As I expected, the Astro 7 could not keep up with the TEC180's 7.1" of unobstructed glass. However, it wasn't what I would characterize as a blowout - things were just a bit better in the 180 on planetary and lunar. Given the low contrast that DSOs have, the 7's obstruction did not handicap the views compared to the TEC180, and of course it is MUCH easier to transport a Q7 to a dark site than a 36 lb, 4 ft long refractor!

 

Unfortunately I did not do any direct comparisons on double stars, but I will say the apo refractors were fantastic at splitting doubles without any acclimation time. In order to cleanly split the double-double in Lyra, the Q7s had to be well acclimated. From a practical standpoint, all this means is that the apo's do better on spur-of-the-moment observing.

 

Sam


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#8 JMKarian

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Posted 24 February 2021 - 09:37 PM

JimP
Have had my Astro 7 mounted in a side-by-side with an AP 155 on an 1100 AP mount. They are quite complimentary, and I especially enjoyed the duo during Spring DSO season. Similar experiences to Codbear (Sam), with the quartz Astro 7 being the real standout on splitting doubles.

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#9 RMay

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Posted 25 February 2021 - 01:11 AM

That’s a magnificent setup. May you continue to always be amazed by the places you’ll visit at the eyepiece...

Ron
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#10 Mike Allen

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Posted 25 February 2021 - 08:23 AM

JimP
Have had my Astro 7 mounted in a side-by-side with an AP 155 on an 1100 AP mount. They are quite complimentary, and I especially enjoyed the duo during Spring DSO season. Similar experiences to Codbear (Sam), with the quartz Astro 7 being the real standout on splitting doubles.

My goodness, what a wonderful rig.  Congratulations.



#11 sqrlman

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Posted Today, 01:45 AM

JimP
Have had my Astro 7 mounted in a side-by-side with an AP 155 on an 1100 AP mount. They are quite complimentary, and I especially enjoyed the duo during Spring DSO season. Similar experiences to Codbear (Sam), with the quartz Astro 7 being the real standout on splitting doubles.

John,

 

Which telescope gives the brighter image?

 

Steve



#12 JMKarian

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Posted Today, 05:28 AM

John,
 
Which telescope gives the brighter image?
 
Steve


Steve,
As the fields/magnifications vary depending on which eyepiece/scope combination is chosen - they are pretty much the same to my 70 year old lens-refracted right eye. Contrast edge goes to the Astro 7.

John
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