Takahashi FC-100DC vs DL Comparison

[John]

Apologies if this has been posted before but this is the first time that I've come across this comparison by Roger Vine. Two of our members here were also involved I'm pleased to see - because it's their scopes that are being compared by Roger

I guess the result is what I would have expected: too close to call except in extemis when the small difference in focal ratio (not optical quality) shows very slightly:

http://scopeviews.co.uk/TakFC100s.htm

It's nice that Roger has had the chance to get his hands on a DL at last

Thanks also to Mike and Paul for allowing the use of their scopes for this

[festoon]

Thanks for posting this John...I think it's a really nice conclusion....I hope one day to do a similar comparison myself  

[Stu]

Thanks John, interesting read and based on a brief comparison with Gavin's DL it seems in line with my impressions.

Ultimately the DL will provide slightly better views under excellent conditions at the cost of a longer heavier tube. Given that much of my observing is grab and go the DC suits me fine, but the DL makes total sense for those without that requirement.

[GavStar]

23 minutes ago, Stu said:

Thanks John, interesting read and based on a brief comparison with Gavin's DL it seems in line with my impressions.

Ultimately the DL will provide slightly better views under excellent conditions at the cost of a longer heavier tube. Given that much of my observing is grab and go the DC suits me fine, but the DL makes total sense for those without that requirement.

Yes Stu, as a result of that comparison I decided to sell my DL and keep my DF since it’s easier to mount and use as a grab and go with minimal difference in the views.

Edited December 31, 2017 by GavStar

[John]

As I've said before, if I hadn't had the Vixen ED102SS F/6.5 then I'd have probably gone for a DF as well. Two 4 inch refractors is hard to explain to my other half as it is but a least the splindly DL looks sufficiently different from the Vixen to get away with it (just)

I've actually got the Vixen outside right now dodging the clouds and clocking some New Year's Eve doubles - cracking scope for an FPL-51 F/6.5 doublet. Well done Vixen

Happy New Year to All !!!

 

[mikeDnight]

It was a very memorable night! The moon was insanely sharp (Antoniadi 1) which gave both scopes a perfect opportunity to show their best. It was a rollercoaster of excitement as we tried several very high end eyepieces in both the DL and the DC, and were genuinely stunned by the sharpness in each. We were all equally stunned when the binoviewers using cheap eyepieces gave an even sharper view than the superlative 5mm TMB Super mono. That was a real game changer moment for all of us!

We came back in the house for an hour or so late in the evening to indulge in a wonderful Indian Takeaway. Afterwards we returned to the scopes which had been left outside. Jupiter by this time had had chance to rise to a reasonable height. Both scopes were aimed at the planet but the DC, for the first time ever, gave a washed out view. I thought initially it was a fogged up lens but not so. The DL, which was situated about 25 feet away gave a truly mouthwatering view with detail on detail. I was a bit peeved at the poor view through the DC, as it was definitely out of character. The DC is a scope with a proven track record but it wasn't having any of it at this point.

The following week Richard again was on his way to observe with us, however he got stuck in traffic and after waiting an hour without moving, he phoned to say he'd had to turn back. It was a shame he couldn't make it on that occasion as the tables were turned on the DL. Again both scopes were placed in the same positions as the week before, but this time it was the DL that gave the unusually blurry image, while the DC soared ahead, showing razor sharp high definition, detailed views of the jovian belts and zones. Paul reckoned it didnt count as Richard wasnt there to witness it, but it settled my mind concerning the excellence of the DC. The only conclusion concerning the blurry image on both occasions that we came to was a probable local heat plume, as both scopes had played together on many occasions quite nicely previously and since. 

I know you guys like pics, so here are the scopes we played with on that first evening. 1st two Paulastro's DL, 2nd two Rodger Vines beautiful 76mm Tak, and the last three are of the DC. 

[Ibbo!]

Wonder how my ancient and a little battered (but loved ) FS102 would fair is this company.

[John]

30 minutes ago, mikeDnight said:

...Jupiter by this time had had chance to rise to a reasonable height. Both scopes were aimed at the planet but the DC, for the first time ever, gave a washed out view. I thought initially it was a fogged up lens but not so. The DL, which was situated about 25 feet away gave a truly mouthwatering view with detail on detail. I was a bit peeved at the poor view through the DC, as it was definitely out of character. The DC is a scope with a proven track record but it wasn't having any of it at this point.

The following week Richard again was on his way to observe with us, however he got stuck in traffic and after waiting an hour without moving, he phoned to say he'd had to turn back. It was a shame he couldn't make it on that occasion as the tables were turned on the DL. Again both scopes were placed in the same positions as the week before, but this time it was the DL that gave the unusually blurry image, while the DC soared ahead, showing razor sharp high definition, detailed views of the jovian belts and zones. Paul reckoned it didnt count as Richard wasnt there to witness it, but it settled my mind concerning the excellence of the DC. The only conclusion concerning the blurry image on both occasions that we came to was a probable local heat plume, as both scopes had played together on many occasions quite nicely previously and since....

 

So what Roger says, and annotation that you have on the sketch in his report is incorrect then - it was a heating plume rather than a fogged DC objective that caused the slightlly improved DL vs DC views of Jupiter ?

That seems an odd inconsistency for one of Rogers reports to include

 

 

[John]

23 minutes ago, Ibbo! said:

Wonder how my ancient and a little battered (but loved ) FS102 would fair is this company.

I'm sure it would do very well, as long as it's not pointing through a heating plume

[mikeDnight]

7 hours ago, John said:

So what Roger says, and annotation that you have on the sketch in his report is incorrect then - it was a heating plume rather than a fogged DC objective that caused the slightlly improved DL vs DC views of Jupiter ?

That seems an odd inconsistency for one of Rogers reports to include

 

 

Hi John,

Rodgers review reflects accurately what he saw, and he spent a good six or seven hours to draw his conclusions after truthfully examining both scopes with a most critical and experienced eye. I've observed with him on a number of occasions and respect him greatly. It's a real shame he couldn't make it over on the following weekend! The sketch is spot on, and the DL delivered a view that i never saw in my FS128 or my FS152, showing a level of detail that is truly unimaginable through a 4" aperture scope. The drawing is actually only a representation of what I saw and doesn't actually convey accurately enough just how good the view was. I genuinely believe the DL is the world's finest 4" refractor readily available today!

It was an unusually steady night and there was no shimmer whatsoever. All I can imagine is that there was some heat from somewhere that was rising steadily. Both scopes give great views of Jupiter, but on the first night the DC simply didn't. I suggested to Roger it must be due to fogging, but on examination of the lens there was no indication of it misting up. The weekend after was another really top class night and this time the opposite happened. It's somewhat baffling, but as my eastern and southern view, although pretty good, looks over the town, I imagine it could have been heat from a chimney or something. I suspect my neighbours chimney, which the DC was looking over on the first night and the DL was looking over the following weekend. Prior to the session on Jupiter on that first night when Rodger was with us, both scopes were unbelievably sharp, so much so in fact that Rodger was completely wowed by just how good both scopes performed. I also remember him commenting on the obvious lack of any CA in the DC, which he obviously expected to be much more evident. So when Rodger says the DC showed more CA, it has to be remembered he has an extremely critical eye for comparing the optical differences. 

[festoon]

And just to add to the pictures, here is a picture Paul's old FC100DL in its new home and with its new finder scope....I cannot wait for Mars later this year and Jupiter to be a bit higher in the sky to use it on them. 

Happy new year to everyone  

 

[Timebandit]

 

 

Interesting. From the feedback from Mike. It seems anyone with a DC or DL should be investing in some Binoviewers. Apart from the seeing conditions, Binoviewers seem to be at the top of the list to get the best out of your Tak DC or DL.

And best of all a reasonable pair of binoviewers and a couple of Ortho or plossl will not break the bank. ?

 

 

[mikeDnight]

12 hours ago, John said:

" slightlly improved DL vs DC views of Jupiter ?"

That seems an odd inconsistency for one of Rogers reports to include

 

 

On Jupiter that evening, the difference wasn't slight, it was vast, as if the DC wasn't in focus. Very strange! The DC was using a pair of 16.8mm Orthoscopics and not 17mm plossls, and the DL a pair of 19mm extra flats. And as far as I'm aware, the DF has a fixed dew shield and not a retractable one. Its not always easy to remember all the details when writing up reports and even the best reviews can sometimes have the occasional blip! 

I did initially say to both Paul and Rodger that it must be due to a fogged lens, though the outer element didn't appear to be fogged up. I assumed at that point that it must be something on one of the inner surfaces. It was really only the following weeks session that seemed to point to a local heat source. Whatever it actually was it was weird!! 

I never lose my temper or swear while observing, not even when Paul's dear wife used my eyepiece case full of Televue and Pentax eyepieces as a chock for her car. However, if this had been my first view of a planet through the DC, I would certainly have sent it back with a stiff note!  Having seen the scope perform outstandingly so on many previous occasions I had to just bide my time for a probable answer.  

[paulastro]

Mmm, funny how memory plays tricks on you.  I could have sworn that it was your eye that was fogged up Mike

I have to admit, when my wife drove over your eyepiece box you showed tremendous self control.  I put this down to you being in shock .

[John]

Thanks for the further background information Mike

I agree that it is very disconcerting when a piece of equipment suddenly peforms in a very out of character manner.

I have experienced this a few times and there has invariably been a reason such as the central heating plume which comes out of the side vent from our house - get that between you and your target in the dark and it appears that your objective might be melting !

Another "classic" was when I was using the 6mm Ethos eyepiece with the ED120 to observer Jupiter a while back. The view was very washed out although the principle features could be made out. I thought something had fogged up or that thin clouds had drifted across but no, I'd left the translucent plastic dust cap on the 1.25" barrel part of the hybrid Ethos barrel (I had it in the scope in 2" mode). Considering the view was through a mm of soft plastic it was surprisingly that I could see any Jovian detail !. I don't recommend this as an effective "Jupiter filter" technique

Here's to clear dark skies in 2018

 

[paulastro]

2 hours ago, festoon said:

And just to add to the pictures, here is a picture Paul's old FC100DL in its new home and with its new finder scope....I cannot wait for Mars later this year and Jupiter to be a bit higher in the sky to use it on them. 

Happy new year to everyone  

 

Good to see you're looking after it, and I hope you have many opportunities to observe Mars with it.  Happy New Year to you too, and to all other SGLers of course. 

[Stu]

46 minutes ago, Timebandit said:

 

 

Interesting. From the feedback from Mike. It seems anyone with a DC or DL should be investing in some Binoviewers. Apart from the seeing conditions, Binoviewers seem to be at the top of the list to get the best out of your Tak DC or DL.

And best of all a reasonable pair of binoviewers and a couple of Ortho or plossl will not break the bank. ?

 

 

I think normal Binoviewer peculiarities are just as applicable with these scopes as any others. I find them fantastic for white light solar, very good for lunar, but cyclops suits me better for pretty much anything else. I can use my binoviewers natively for low power DSO observing but the jury is still out on whether that is better or not.

I recall observing Sigma Orionis in both the DC and DL at similar times. The DL definitely showed the fourth component more easily on that occasion, but I know that the DC has done better at other times. They are obviously close, but you would expect the longer focal ratio to come into play to give that bit extra on good nights.

Personally I would have observed with similar magnifications so that the views were comparable, rather than the same eyepiece as that is not a level playing field. 

[mikeDnight]

1 hour ago, Stu said:

I think normal Binoviewer peculiarities are just as applicable with these scopes as any others. I find them fantastic for white light solar, very good for lunar, but cyclops suits me better for pretty much anything else. I can use my binoviewers natively for low power DSO observing but the jury is still out on whether that is better or not.

I recall observing Sigma Orionis in both the DC and DL at similar times. The DL definitely showed the fourth component more easily on that occasion, but I know that the DC has done better at other times. They are obviously close, but you would expect the longer focal ratio to come into play to give that bit extra on good nights.

Personally I would have observed with similar magnifications so that the views were comparable, rather than the same eyepiece as that is not a level playing field. 

Hi Stu,

If Peter Drews bino magnification method is bang on accurate, the DC with the 16.8 orthos would be working at X176, while the DL with the 19mm extra flats was working at X189. Certainly from mono comparisons it seems to be fairly accurate. Although it was a significant magnification difference, it was as close as we could get the two powers at that time.

I was looking at the moon a few days ago with the 16.8 ortho's, then I changed to a pair of 15mm LV's I've just acquired. The slight power increase meant the difference between seeing the central rille along the Alpine Valley with certainty in the 15mm's and just getting a hint of it at times in the 16.8 ortho's. It can unbalance a comparison, leading to a misconception of a scopes abilities if the powers don't match exactly, but getting that level playing field isn't always easy.

Twice now I've had chance to grab a DL for myself, but it would have meant parting with my beloved DC first, which is something I couldn't bare to do. Perhaps I'm soft in the head!?

[Stu]

2 minutes ago, mikeDnight said:

Hi Stu,

If Peter Drews bino magnification method is bang on accurate, the DC with the 16.8 orthos would be working at X176, while the DL with the 19mm extra flats was working at X189. Certainly from mono comparisons it seems to be fairly accurate. Although it was a significant magnification difference, it was as close as we could get the two powers at that time.

I was looking at the moon a few days ago with the 16.8 ortho's, then I changed to a pair of 15mm LV's I've just acquired. The slight power increase meant the difference between seeing the central rille along the Alpine Valley with certainty in the 15mm's and just getting a hint of it at times in the 16.8 ortho's. It can unbalance a comparison, leading to a misconception of a scopes abilities if the powers don't match exactly, but getting that level playing field isn't always easy.

Twice now I've had chance to grab a DL for myself, but it would have meant parting with my beloved DC first, which is something I couldn't bare to do. Perhaps I'm soft in the head!?

Fair enough Mike, it's not easy I agree. In the past I've just used BGOs of different focal lengths to try to get the mags as close as possible.

Whilst I'm not in a position to get a DL even if I sold my DC (given the premium), I feel the same as you. The convenience and ease of use of the DC over the additional length and weight of the DL outweighs the small performance benefit. A DL would be too much for my AZGTi mount which is seeing a lot of use currently.

[festoon]

33 minutes ago, Stu said:

The convenience and ease of use of the DC over the additional length and weight of the DL outweighs the small performance benefit. A DL would be too much for my AZGTi mount which is seeing a lot of use currently.

It's really funny - as you say I would really like to put my 100dl on an AZGTi as it must be so fast to set up....but you can't have everything  

[Stu]

7 minutes ago, festoon said:

It's really funny - as you say I would really like to put my 100dl on an AZGTi as it must be so fast to set up....but you can't have everything  

Yes, a shame, but I think it would probably be just that bit too much for it, particularly at high powers where you need it to be rock steady. I use mine on a Gitzo tripod, the original is certainly not up to it.

[AstroSylv1]

The DL is still available, from the second run...

[John]

1 hour ago, disciplus55 said:

The DL is still available, from the second run...

Indeed it is:

 

[AstroSylv1]

Yes, I saw one at La Clef des Étoiles in Toulouse (France)...

[25585]

Very hard to choose indeed!

That the DF has a sliding dew shield is another point in its favour, along with the beefier focuser. My Equinoxes and Genesis have that kind, and it's a greater benefit than a screw on/off type, apart from rigid OL protection.

The DL has an allure all its own though, and the attraction of using longer FL eps with it, so increasing the range of better eye relief optics usable.

As far as TFOV, in real life viewing, how much increase is there using the F7.5 models?

Which scope would be better for an Astro Physics 2 inch diagonal?