49 replies to this topic

[vkhastro1]

I presently own a TeleVue SDF refractor.

I have the opportunity to upgrade to a TeleVue 101.

 

I am very satisfied with the views through the SDF.

Is it worth the upgrade to the TV101 or wait for a NP101 (which would be more expensive) ?

[GGK]

Here’s another thread with some details on that comparison:

https://www.cloudyni...vs-genesis-sdf/

Gary

Edited by GGK, 28 May 2024 - 04:58 PM.

[Phillip Creed]

I presently own a TeleVue SDF refractor.

I have the opportunity to upgrade to a TeleVue 101.

 

I am very satisfied with the views through the SDF.

Is it worth the upgrade to the TV101 or wait for a NP101 (which would be more expensive) ?

Goooooood question.  I've owned the OG (Original Genesis.  Yes...commence eye rolling), the f/5.4 SDF version of The Genesis Device and currently have the NP101 (non-IS).  My SDF had just a slight amount of CA on the very brightest stars, but I've heard the TV101 is color-free.  But I've never owned nor looked through the TV101.

Having owned both the SDF and the NP101, I can say the views are much more similar than different.  You're not really gaining much visually, and I'd imagine even less in going from an SDF to a TV101.

If you're looking to image at some point, definitely get the NP101.  The SDF and TV101 aren't flat enough for today's tiny digital pixels.  The older (discontinued) non-IS version of the NP101 is MUCH cheaper on the used markets and sometimes pops up for $2,000 or less.  I use my non-IS NP101 with my 533MC-Pro and...well...it just works:

https://www.astrobin.com/q00sxi/

Clear Skies,

Phil

Edited by Phillip Creed, 29 May 2024 - 07:54 AM.

[vkhastro1]

Thanks Phil.

 

I am strictly visual.

The TV NP101 non-IS version rarely if ever come up for sale in my area of Canada.

Definitely prefer local deal within driving distance.

Purchasing from outside of Canada is a no-go due to increased cost of shipping, poor CDN $ to US $ + Canadian Customs on $CDN conversion - 13%.

[Phillip Creed]

If you're sticking to visual observing, I'd stick with the SDF unless the TV101 you're looking to acquire is priced comparably to what you can sell your SDF for.  There is considerable aftermarket price variability on the original f/5 Genesis, f/5.4 SDF Genesis and TV101.

Sometimes you can get crazy deals and sometimes they're just listed too high.  I've seen recent SDF listings wanting more than what I paid for my NP101, but I've also seen TV101's go for less than going rate for an SDF.
 

Clear Skies,

Phil

Edited by Phillip Creed, 29 May 2024 - 08:54 AM.

[alnitak22]

Goooooood question.  I've owned the OG (Original Genesis.  Yes...commence eye rolling), the f/5.4 SDF version of The Genesis Device and currently have the NP101 (non-IS).  My SDF had just a slight amount of CA on the very brightest stars, but I've heard the TV101 is color-free.  But I've never owned nor looked through the TV101.

Having owned both the SDF and the NP101, I can say the views are much more similar than different.  You're not really gaining much visually, and I'd imagine even less in going from an SDF to a TV101.

If you're looking to image at some point, definitely get the NP101.  The SDF and TV101 aren't flat enough for today's tiny digital pixels.  The older (discontinued) non-IS version of the NP101 is MUCH cheaper on the used markets and sometimes pops up for $2,000 or less.  I use my non-IS NP101 with my 533MC-Pro and...well...it just works:

https://www.astrobin.com/q00sxi/

Clear Skies,

Phil

I’d agree it just works….that’s an awesome picture!

[Phillip Creed]

I will say this -- VKHAstro1, don't sell that SDF if you find a more capable scope.  Just save up for the new scope.  Selling my SDF was, bar none, the stupidest decision I've EVER made in this hobby.  If I could find a cheap SDF or TV101 that someone's letting go at an ill-advised low price, I might snap one up just for general visual use.

And I'm admittedly someone who's always sold old scopes to pay for new ones.  But parting with the SDF still hurts to this day.  The SDF is that good.

Some will say, "it's not hard to find a cheaper 4" ED doublet that can match the SDF's color correction."  They're not wrong.  But your standard 4" ED doublet can't squeeze out a 5°-FOV, which under dark skies is an absolute mind trip.

Clear Skies,

Phil

Edited by Phillip Creed, 30 May 2024 - 08:04 AM.

[vkhastro1]

Just an update:

 

With Trump’s tariffs and Canada’s 25% tariff retaliation, $CDN to $US at nearly 45%, shipping, basic import GST purchasing any astronomy items from the USA is extremely prohibitive. Have to look for Canadian opportunities.

 

More CN input would be appreciated concerning the following 2 options (again only visual) from my existing TV SDF for basically the same price:

Both are available for in person pickup within reasonable driving distances, so no issues with possible mis-collimation due to shipping.

 

1. TeleVue TV101 OTA (single rate focuser) with case/TV 2” Everbrite star diagonal + Gibraltar mount 

or 

2. TeleVue NP101 (single rate focuser) with case only

I am leaning to option 1 for the following reasons:

I don’t need the 2” Everbrite star diagonal or the Gibraltar mount.

Both can be sold to reduce the cost of purchase of TV101.

 

Do a shootout between the TV 101 and my current TV SDF.

(My current SDF easily does 200X without breaking a sweat).

The TV101 should be the better scope optically.

 

Any thoughts or input would be appreciated.

 

Thx,

Gary 
 

Edited by vkhastro1, 17 March 2025 - 05:32 PM.

[Dave Novoselsky]

Thanks Phil.

 

I am strictly visual.

The TV NP101 non-IS version rarely if ever come up for sale in my area of Canada.

Definitely prefer local deal within driving distance.

Purchasing from outside of Canada is a no-go due to increased cost of shipping, poor CDN $ to US $ + Canadian Customs on $CDN conversion - 13%.

If you are strictly visual and having owned both my opinion is there is no appreciable “upgrade”.

[Spikey131]

 

“I am very satisfied with the views through the SDF.”

‘Nuff said.  Keep it.

 

I think the difference between the SDF and TV101 is incremental, and you may not notice much difference.

 

You might notice a difference with the NP101.

 

Another thought:  call Tele Vue.  They love to talk about their stuff, and would give unbiased opinions.  You might even get Al on the phone.

[vkhastro1]

Part of the problem is the astronomy “itch”.

Have not done any observing for almost 3 months (other than hand-held binoculars) due to a very long Canadian winter - tons of snow with cold to very cold temperatures. 
Thoughts of spring gets your mind “reved up”.

 

Most of my observing is done on my back deck under Bortle 5ish skies.

I have access to Bortle 4 within 10 minutes drive.

Not really dark enough skies to take full advantage of the short f/ratio of any of the TV SDF, 101 or NP101 scopes.

In my SDF with an exit pupil of say 5mm the background sky is dark gray not black.

With longer exit pupils the skies definitely get more washed out.

I also own a Tak FS102 f/8 OTA - definitely more contrasty with darker background than the TV SDF at the same exit pupils maybe because of the reduced # of lens in the optical train ( 2 vs 4) and the “fluorite magic”.

Maybe I should “refocus”.

[areyoukiddingme]

I have never tried either an SDF or the newer NP101.

 

But I've now compared my TV101 with my AP92 Stowaway. On the planets, the Televue is better with the extra 10mm of aperture.

 

The AP is quicker to cool and the power can be cranked high quickly, but once cooled so does the 101.

 

My guess is that there's going to be very little visual difference between the 101 and the SDF you have, and I suspect they are about the same size and weight.

 

I'd be looking at the NP if I wanted to upgrade.

 

Looking through the old threads was informative and confirms what Phil had to say. For example, I know Jon still has his NP101, but I'm not so sure about the 120mm (he can chime in, but I seem to recall him saying he sold it). 

 

For me personally, I have 80mm, 92mm, and the 101.6 TV 101, and while it would be rational to sell the 80 and 101 and just keep the 92, I can't bring myself to do it. I think I'll really miss both if I sell them, and that's with the AP being as good as you can get for a small refractor.

[Wildetelescope]

I have never tried either an SDF or the newer NP101.

 

But I've now compared my TV101 with my AP92 Stowaway. On the planets, the Televue is better with the extra 10mm of aperture.

 

The AP is quicker to cool and the power can be cranked high quickly, but once cooled so does the 101.

 

My guess is that there's going to be very little visual difference between the 101 and the SDF you have, and I suspect they are about the same size and weight.

 

I'd be looking at the NP if I wanted to upgrade.

 

Looking through the old threads was informative and confirms what Phil had to say. For example, I know Jon still has his NP101, but I'm not so sure about the 120mm (he can chime in, but I seem to recall him saying he sold it). 

 

For me personally, I have 80mm, 92mm, and the 101.6 TV 101, and while it would be rational to sell the 80 and 101 and just keep the 92, I can't bring myself to do it. I think I'll really miss both if I sell them, and that's with the AP being as good as you can get for a small refractor.

I have 2 different 80 mm a 90, a 102 and a 105, Lol. Rational has nothing to do with it. If you had told me 20 years ago I would have MOST of the scopes in my signature, I would have told you you were MAD.  It is a hobby. If it makes you happy that is what matters!:-) In my case, each of them has a different history, and all but one 80 mm would be considered a classic of one sort or another. I don't drink and I don't smoke, so telescopes are my one vice.    Plus, I can populate my own star party at out reach events.  And I do not hold a candle to some around here;-)  

 

Cheers!

 

JMD
 

[Jon Isaacs]

A few random thoughts:

 

- I did sell my 120 mm Eon. On the planets and double stars the extra 18 mm of aperture provided better views. I sold it because I wasn't using it.. For the planets and double stars, if I wanted a better view, I was using my 10 inch Dob.

 

I've only looked through an SDF or a TV-101 a couple of times so I have little to add. The SDF was introduced in 1993, the 101 in 1996 and the NP-101 in 2001. Things were changing quickly back then in terms of ED glasses and APOs. It seems like with the NP-101, they got it right. Since then, the only change is the IS model which provides a larger illuminated field. 

 

Jon

[RyanAstroMan]

The SDF is my favorite and most used scope for visual, I've never tried the TV101 or NP101 but I think the differences would be very minimal, and if you already have a TAK FS102, than you have a good 4 inch range covered quite well. The direction I would choose would be something like a TAK TSA-120.

[vkhastro1]

The SDF is my favorite and most used scope for visual, I've never tried the TV101 or NP101 but I think the differences would be very minimal, and if you already have a TAK FS102, than you have a good 4 inch range covered quite well. The direction I would choose would be something like a TAK TSA-120.

I have a binofriendly version Tak FS128 with Starlight Instruments FT micropinion upgrade.

I have gotten into more binoviewer and large binocular viewing.

As mentioned, I am mainly a Deepsky observer.

The TV SDF with Orion linear binoviewer with ES 16mm 68° eyepieces will yield a FOV of 2° @ 34X

My APM 70mm SD 90° binoculars with 24mm Panoptic will yield a FOV of 4° @ 17x

These two will cover most of my preferred views - widefield and semi-widefield with both giving the option to increase the magnification as needed.

The TV SDF image with binoviewer is basically the same as a 70mm Binoscope at the same exit pupil.

I definitely take out the APM 70mm binoscope more than the TV SDF (almost making the TV SDF redundant which is a real shame).

 

However:

 

The opportunity of purchasing either the TV101 or NP101 rarely comes up in Canada and to have either option locally is basically “never”.

Still on the fence !!

[vkhastro1]

Finally had my 1st relatively clear night (high cirrus) with quite a bit of fully clear skies + co-operating weather temperature for a shootout - just wish the conditions were better but will have to take what I have.

 

Setup the TV SDF on Stellarvue M2C alt-Az/column/handle on an Oberwerk wood tripod.

VS

APM 70mm SD 90° binoscope on APM alt-Az Gabel mount on Hercules Quickset geared heavy duty tripod.

 

Full evaluation of the SDF in mono and binoviewer mode (Orion linear).

My skies were totally washed out with TV 35 Pan (exit pupil = 6.5mm) - perfect stars to edge

Tried Pentax 23mm (showed some EOFB (exit pupil = 4.3mm) - again grey background - nearly perfect stars to edge

Next Pentax 16.5mm (exit pupil = 3.1mm) much darker background - basically edge perfection 

ES 16mm 68° - perfect to edge

ES 16mm 68° in Orion linear binoviwer achieving a TFOV of 2° but only the inner 60% was in perfect focus and really not acceptable (IMO) at the edges - that experiment was a failure for sure

I will need to try a different binoviewer (Zeiss) with a OCS to re-evaluate the SDF in binoviewer mode.

Couldn’t get past 9mm TV Nagler due to poor seeing conditions.

I know this SDF has great optics - tested to 3mm - 180X under excellent steady conditions.

 

The APM 70 with TeleVue 24mm Panoptics (16.7X @ exit pupil = 4.2mm AFOV = 4°) had a more engaging view of the Double Cluster and M42 region compared to the SDF mono view with Pentax 23mm (23.5X with TFOV = 3.5°).

Really similar flat view and for some reason had a slightly darker background plus the true binocular summation effect.

Definitely preferred the APM70 view

 

I don’t think having a TV101 or NP101 would have made much of a difference compared to the SDF.

[RichA]

If you are strictly visual and having owned both my opinion is there is no appreciable “upgrade”.

Notably less colour error.  SDF still falls into the "semi-apo" realm though it is superior to the Genesis.  The TeleVue's are fast enough so that colour correction needs higher-end glass.  This does not detract from the quality of the SDF as far as sharpness goes, both scopes are very good in that regard. 

[Spikey131]

Notably less colour error.  SDF still falls into the "semi-apo" realm though it is superior to the Genesis.  The TeleVue's are fast enough so that colour correction needs higher-end glass.  This does not detract from the quality of the SDF as far as sharpness goes, both scopes are very good in that regard. 

The SDF has “special dispersion” (SD) GP glass in the objective and fluorite (F) in the Petzval corrector.  Hence, has “high end glass”.  I believe the color correction is similar to the TV101, but it was expensive to make.

 

If you have one of these, please correct me if I am wrong.

[25585]

http://www.company7....opes/tv101.html

[Tyson M]

Unless you own both scopes side by side on the same night- it's virtually impossible to tell. Since the apertures are the same, what are you comparing?

Color error, optical quality? Both? Color error is virtually a wash, but a newer scope might be better corrected [np101] but older scope might have a better figure.

So ask yourself, what do you primarily use the scope for? Wide fields with bright stars? Maybe you want better color correction [re: maybe the np101 but hardly noticeable I reckon].

Are the optics bad on your current scope? If not, I'd keep it. If you got money to burn and have the itch, buy a second scope and compare them. Until you have both scopes side by side, comparing these virtually identical scopes is going to be hard

Edited by Tyson M, 20 March 2025 - 09:30 AM.

[RichA]

The SDF has “special dispersion” (SD) GP glass in the objective and fluorite (F) in the Petzval corrector.  Hence, has “high end glass”.  I believe the color correction is similar to the TV101, but it was expensive to make.

 

If you have one of these, please correct me if I am wrong.

In that era, the 101 is closer to my FS-102 (Takahashi) and noticeably better than the SDF.  Meade's ED102's had better colour correction than the SDF as well.  But remember the TeleVue's are much faster, have a flatter field than either the Meade or the Takahashi so the correction of the 101 is pretty remarkable.  The Takahashi FS-102/Meade ED102 are better compared to the TV 102.  Takahashi's superior, fast telescope (FSQ106) also costs a lot more than any of these scopes.

[vkhastro1]

Are the optics bad on your current scope? If not, I'd keep it. If you got money to burn and have the itch, buy a second scope and compare them. Until you have both scopes side by side, comparing these virtually identical scopes is going to be hard

The optics on my TV SDF are perfectly collimated - beautiful inside and outside of focus.

180X is easy with snap focus (under excellent but rare for me conditions).

 

I don’t know about other observer’s thoughts but I seem to be under whelmed by what I am seeing in a 4” scope.

As other members have stated, no matter how good the 4” optics are it is only a 4” aperture.

 

The TV SDF wide angle views are nice but my APM 70SD 90° binoscope puts up a better view.

The larger Deepsky objects ie North America Nebula, M31, Double Cluster, M45 etc look great in the APM 70.

But the vast majority of Deepsky objects are nicely framed in a minimum of TFOV of 1° and the magnification may be increased as desired from there for better “framing”.

Here are the advantage of larger optics - more light grasp and better resolution.

M13 resolution in the 4” just doesn’t cut it compared to the view in my smallish Meade SN8 f/4 Dob. My larger Dobs take the views to another level again.

[Tyson M]

The optics on my TV SDF are perfectly collimated - beautiful inside and outside of focus.
180X is easy with snap focus (under excellent but rare for me conditions).
 
I don’t know about other observer’s thoughts but I seem to be under whelmed by what I am seeing in a 4” scope.
As other members have stated, no matter how good the 4” optics are it is only a 4” aperture.
 
The TV SDF wide angle views are nice but my APM 70SD 90° binoscope puts up a better view.
The larger Deepsky objects ie North America Nebula, M31, Double Cluster, M45 etc look great in the APM 70.
But the vast majority of Deepsky objects are nicely framed in a minimum of TFOV of 1° and the magnification may be increased as desired from there for better “framing”.
Here are the advantage of larger optics - more light grasp and better resolution.
M13 resolution in the 4” just doesn’t cut it compared to the view in my smallish Meade SN8 f/4 Dob. My larger Dobs take the views to another level again.

I agree that a 4" scope can be underwhelming, especially in the city. I've been hesitant to buy another, although I want the wide fields of viewing for a dark site.

My grab and go mount is the limitation here, but I think I may go to a 115-120mm scope.

For a dark site a flat field 4" apo would be amazing, but I agree it does have overlap with your binoculars.

[vkhastro1]

I agree that a 4" scope can be underwhelming, especially in the city. I've been hesitant to buy another, although I want the wide fields of viewing for a dark site.

My grab and go mount is the limitation here, but I think I may go to a 115-120mm scope.

For a dark site a flat field 4" apo would be amazing, but I agree it does have overlap with your binoculars.

Exactly my thoughts - with the TV 101SDF, Tak FS102 and Altair 102mm f/12 FPL bino-friendly doubletI already have the 4” APO size covered. The longer f/ratios of the Tak and Altair (especially) have much higher contrast and enjoy their views over the TV 101SDF.

I have a Skywatcher 120 FPL53 and Tak FS128 covering the 5” APO size covered.

No reason to overthink this one !