The Questar 3.5", like most catadioptric telescopes, has a wide range of focus adjustments and should work with any eyepiece that physically fits in the diopter adapter. The built in Questar finder has a small range of focus adjustment limited by the diopter adapter. Many 3rd party eyepieces will not come to focus in the finder.

This table summarizes eyepiece finder comparability information from several sources. If your vision is not perfect and you use the Questar without corrective lenses, you results may differ depending on the correction you require and whether the person making the report had corrected vision.

There is also a slight difference in the height of the Questar and TeleVue diopter adapters which may also affect results. The modern Questar 1.25" diopter adapter with Questar/Brandon eyepiece threads and two locking screws is required if both Questar and 3rd party eyepieces will be used with a single adapter. Many of these results are believed to have been obtained with the Questar adapter.

Because of the unknown testing conditions and variation in personal viewing preferences with regard to vision correction, consider this only a rough guide and verify that a particular eyepiece will focus in the finder with your own vision.

Vendor	Model	Size	Focus	Barrel	Source
Celestron	Finder cross-hair (orange)	8x50	Yes	0.965	2
Celestron	silver top Plössl	17	Yes	1.25	1,2
Edmund		1-1/8"	Yes	1.25	1,2
Kinoptik/Clave	Plössl	16,10,8	Yes	1.25	2
Questar/Vernonscope	Brandon	32,24,16,12,8	Yes	1.25	1,2
TeleVue	DeLite	18.2,15,13,11,9,7	Yes	1.25	4
TeleVue	Delos	12,10,8,6	Yes	1.25	4
TeleVue	Nagler	4.8	Yes	1.25	1,2
TeleVue	Panoptic	15,19	Yes	1.25	1,2
TeleVue	Panoptic	19	Yes	1.25	4
TeleVue	Plössl	32,26,25,20,21,17,13,10.4	Yes	1.25	1,2
TeleVue	Plössl	25,20,15,11,8	Yes	1.25	4
TeleVue	wide	19	Yes	1.25	1,2
Unitron	Huygens	25	Yes	0.965	2
Unitron	Kellner	18,12.5	Yes	0.965	2
University	(70's) Koenig	16	Yes	1.25	1,2
University	(70's) Pro Series Ortho	28,10.2,6.8	Yes	1.25	1,2
Bausch & Lomb	Achromatic Symmetrical Plössl	30, 18, 12.7	Out	1.25	7
Cave	Ortho	25	Out	1.25	1,2
Celestron	Erfle	20	Out	1.25	1,2
Celestron/University	Kellner	40,25,25(reticle)	Out	1.25	1,2
TeleVue		40	Out	1.25	1,2
University	Koenig	12	Out	1.25	1,2
University	Professional Ortho	10.2, 6.8	Out	1.25	7
Vernonscope	Brandon	7/8",3/4"	Out	1.25	1,2
Zeiss	44 41 32	25	Out	0.965	6
Baader	Classic OR	6	No	1.25	6
Baader	Genuine OR	10	No	1.25	6
Cave	Ortho (OrthoStars?)	16,10	No	1.25	1,2
Celestron	Ortho reticle	12.5	No	1.25	2
Celestron	Ultima	35,30,18,12.5	No	1.25	2
Clave	Plössl	20,10,6	No	1.25	1,2
Edmund	RKE	28,21,15	No	1.25	1,2
Fujiyama	Genuine OR	12.5	No	1.25	6
Meade	Erfle	12.4	No	1.25	1,2
Meade	RG Erfle	20	No	1.25	1,2
Meade	RG Ortho	7	No	1.25	6
Meade	SuperWide	24.5, 18	No	1.25	1,2
Meade	UltraWide 4000 (rubber grip)	8.8	No	1.25	2
Meade	wide	20	No	1.25	1,2
Orion	LV	9.5	No	1.25	1,2
Pentax	XP		No	1.25	1,2
Pentax	SMC Ortho		No	1.25	2
Pentax	Siebert 7.9 StarSplitter	7	No	1.25	1,2
Pentax	XF	12,8.5	No	1.25	2
Pentax	XW	14,10	No	1.25	1,2
Televue	Ethos	13,10,8,6	No	1.25	4
Televue	Nagler	9,7	No	1.25	2
Televue	Nagler Type 2		No	1.25	2
Televue	Nagler Type 4	13,12	No	1.25	2
Televue	Panoptic	22	No	1.25	2
Televue	Radian	14,18	No	1.25	1,2
Televue	zoom	6-3mm	No	1.25	2
TMB	SuperMono	1st run	No	1.25	2
University	Koenig	24	No	1.25	1,2
University	Ortho	12.5,9	No	1.25	2
University	Super Erfle	20,16	No	1.25	1,2
Vixen	Lanthanum	10,5	No	1.25	2
Vixen	LVW	17	No	1.25	3
Vixen	Zoom (no click)		No	1.25	2
Zeiss	Abbbe Ortho-II		No	1.25	2

1. 2002 Yahoo Questar User Group file Qfindlst.txt

2. 2009 Cloudy Nights Questar Forum post by JimK / Skygazer, Posted 01 November 2009.

3. 2016 Yahoo Questar User Group post by Woody Schlom, Post 28045.

4. 2016 TeleVue Questar Adapter Page

5. Eyepieces Used By Questar

6. 2016 Cloudy Nights Questar Forum post by Jon Teets, Posted 22 July 2016.

7. 2020 Cloudy Nights Questar Forum posts by munirocks and davidmcgo August 2020.

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