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Kit for SCT 8in - a couple of dilemmas


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Ok, as you can see in my signature, I already have a 127 Mak. I reckon you are not too surprised to hear that I would like to add another scope. :)

I am practically decided on getting an Evo 8, just in time for the best part of the season where I get to spend quite a few nights at reasonably dark sites. 

Leaving aside some absolute musts (heated dew shield for where I observe, etc), my main dilemmas are as follows:

1. Should I get a focal reducer or upgrade to 2 in diagonal?

The former would turn the scope into f/6.3, but would also add some light to the flight path. It would also make my current eyepieces (workhorses Baader Zoom and the ES 24) work at the current magnifications, but with DOUBLE the exit pupils - whether that is good or bad I do not know, but that would probably mean that the objects would be brighter but the contrast would suffer, correct?) Would 24mm with focal reducer give the maximum TFOV?

The later would, I understand, enable the use of some quality diagonals (clicklock Baader comes to mind), as the 1.25 offer seems a bit flimsy, to be honest. Baader Zoom would also benefit from being used with its 2in adapter, at least when it comes to stability, I guess. ES would have to be used through adapter to 1.25. The scope would get heavier and I would probably have to add  something around 37-40 with 68-72 degrees for wide views.

I understand that this is either-or decision, as the reducer and 2in diagonal do not seem to work together.

I also understand that reducer is particularly beneficial for AP, which I am not interested in...yet. :)

2. If I go for reducer, the matter is clear, I would have to stick with the 1.25 diagonal and something sturdy for visual back, what would you recommend?

3. If I go to 2 inches, any recommendation on visual back and diagonal and/or low-powered eyepiece?

4. Starsense...makes any sense with Evo, except that it removes the last chore? :)

5. Red dot finder comes supplied, is that any good? If not, what can alternatively be mounted on that little mount the OTA has?

6. What to use for collimation? I understand that the vanilla option are Allen screws. I guess they come in the box, are there any suitable alternatives? Artificial star, too?

Sorry to ask it all in one big pile, since I live outside of the EU, I have to carefully plan my purchases and purchase pretty much all I can in one go.

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Get a 2" diagonal - use both sizes of EP with that.  Focal reducers don't really work (esp. at low mag) on such 'scopes.

Revelation low power EPs are good - I have 50, 42, 30mm.

Starsense - well, alignment is quick and easy after a bit of practice, so save the money.

I like my RDF, and use it in conjunction with a RACI finderscope - a great combo!

Collimation - I use a home-made artifical star, and turn the screws (carefully!) with a crosshead screwdriver.  No special knobs.  Works fine.

Have fun!

Doug

 

 

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I bought the Celestron 2" diagonal to go on my CPC800 and also use the Baader zoom - great combo.

Just a thought, have you considered the CPC800 or are you getting the evo second hand, for roughly the same price you get the stability of the twin arm mount and built in GPS.

Sorry can't comment on the focal reducer as I've not got one.

 

 

 

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Here's some thoughts about your questions:

1. reducer or 2" diagonal?

If C8 is to be your only scope or you can buy a used reducer, then reducer is a good and cost effective way to get started with your present stuffs (assumping filter is 1.25"), the stock diagonal is of optimal size for keeping the right focal length of the scope, your EPs cover the exit pupil range 1,3 to 3.8mm, you can easiler expand it with a simple 32mm plossl and the Baader barlow for better coverage of the exit pupil range.

Reducer flattens the field of C8, get you about the maximum TFOV of a C8 as 2" alternative, the downside is there might be slight vignettting in maximum TFOV since the reducer has only 25mm clear aperture.

2" diagonal will be more costly, adapter to visual back, 2" EP, 2" filters etc. If you know that you're going to have a scope for wide field of view, a short ED refractor ,e,g which I can warm recommend to anyone who has a 8" or larger scope, then you need to take a serious look how would you like to proceed.

2. 1.25" diagonal:

The stock diagonal is a good start, you don't need to rush to uppgrade.

3. 2" diagonal and EP:

A dedicated 2" SCT diagonal (with SC thread) has shorter light path than ordinary 2" diagonal(needs a SC aadapter), but it can't be used in a refractor, so is your decision what suits you best. 2" EP should be something have 46mm field stop (assuming you're after max TFOV with 2" option), 41mm panoptic, 42mm Vixen SLW or 40mm Skywatcher Aero (TS Paragon) are among better choices denping on your preferences.

4. Starsense:

Havan't use it, don't feel the need either.

5. Finderscope:

I've only the Celestrion illuminated RACI, don't feel the need of an RDF.  RACI is good enough fo star hopping and alignment both in  backyard and dark site, illummination is need  in dark site for centering.

6. Collimation:

I replaced the stock screws with better ones because one got crossed during collimation (OBS. replacing them one by one!), crosshead screwdriver is my tool too. Summer white nights are good for collimation when Vega is high. I've tried indoor collimation with flashlit ball bearing too, and it works too.

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Loads of folk say "Starsense, you don't need it". True, but then I have heated seats in my car and I bet the same fine dudes in California and Florida wonder why I need those.

Starsense means I can aim my telescopes in any direction simply with the OTA horizontally aligned with its check mark (fantastically simple with the Evo's easy release clutches). I switch on, wait 10 seconds, insert date/time; go fetch my EP's and by the time I am back it is aligned and ready to GoTo.

Under the UK's cloudy skies, viewing time available is often limited. So why waste time tediously manually aligning multiple stars that you don't actually intend viewing? OK,  it is true that a better buy might be a Televue EP if budget is an issue. But UK retailers are currently  bundling a FREE StarSense with every Evo 8 or 9.25 or HD.Those that take this offer won't regret it. So let's not knock  the luxury route to finding the skies. Some of us prefer a limousine rather than a truck.

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On 15/06/2016 at 19:20, cloudsweeper said:

 

Starsense - well, alignment is quick and easy after a bit of practice, so save the money.

I like my RDF, and use it in conjunction with a RACI finderscope - a great combo!

Collimation - I use a home-made artifical star, and turn the screws (carefully!) with a crosshead screwdriver.  No special knobs.  Works fine.

i hear you. it's either starsense or a much cheaper illuminated reticle eyepiece.

bundling free starsenses? i am aware only of the edge 8 hd evolution bundle...who is bundling it with the evo 8? :)

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All the principle UK retailers were bundling Starsense with the Evo 8 until 31st May under a special deal with the main distributor. Probably trying to offload their stock of Evo 8's before the more expensive Evo HD arrives in July (Er, can the incremental cost of that be justified?). However, even today the Widescreen Centre website shows a Evo 8 with free StarSense for £1,575 , and one can buy on line. 

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one of the few remaining dilemmas...

going 2 inch, should i get SW Aero 40 (68 deg) or Baader Aspheric 36mm (72deg). Aero would get a slightly bigger exit pupil, but still only slighly under 4mm after diagonal upgrade, and a slightly bigger TFOV. Would it vignette? Baader would have even smaller exit pupil, at 3,55 and probably somewhat smaller TFOV. What should I chose as the low power eyepiece? SW is cheaper...

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5 hours ago, BGazing said:

one of the few remaining dilemmas...

going 2 inch, should i get SW Aero 40 (68 deg) or Baader Aspheric 36mm (72deg). Aero would get a slightly bigger exit pupil, but still only slighly under 4mm after diagonal upgrade, and a slightly bigger TFOV. Would it vignette? Baader would have even smaller exit pupil, at 3,55 and probably somewhat smaller TFOV. What should I chose as the low power eyepiece? SW is cheaper...

But worth trying those still advertising these deals on line. Under the UK Sale of goods act, if still advertising this deal it is an "invitation to treat". So if you are able to "accept" this if in the EU they are usually  obliged to honour this. Serbia might be more tricky.

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