orion apex 90 vs apex 102mm

StrifeYun · Post by **StrifeYun** » Thu Oct 12, 2006 6:19 am

hi guys ... now i'm thinkin that i should had gotten the apex 102 instead of the apex 90mm hmmm

what difference in comparison be ?

alot of difference ? or not much ? hhmmm

any comments ?

jermng · Post by **jermng** » Thu Oct 12, 2006 8:59 am

I don't know about the specific difference between the two, but I can only say that this will never end. If you had gotten the 102, you would wonder what difference it has with the Apex 127 ... and the cycle will go on and on ..

I'm not sure if my numbers are right, but I'm just typing this off the top of my head, if I'm wrong, someone do correct me - The minimum jump where a normal amateur can detect a difference between apertures is

3"-5"-8"-12.5"-18".

Some people have detected differences with smaller jumps so your mileage may varry.

Just my 2c.

Post by **acc** » Thu Oct 12, 2006 9:01 am

Noticeable but not a whole lot. Well if you can return it for an exchange...

Tachyon · Post by **Tachyon** » Thu Oct 12, 2006 9:19 am

Hmm.. aperture fever... I suggest at least a 110mm for an observable difference...

StrifeYun · Post by **StrifeYun** » Thu Oct 12, 2006 9:22 am

hmm okay thanks guys haha ... cause i want somethin portable. I din know that the 102mm could be mounted on the min-eq ..... the sales ppl can never ask them much .... k lah ... initially i targeted the 70mm ... then got greedy haha .... dam bought 2many accesories haha ... even got a sun filter haha ......
think jermng is right ... hee ...i must control myself ...
hmm ... i'm thinkin of selling my bushnell voyeger 60mm refrector hee .. any takers ?

i got the meade video output to TV .. hmmm haven't tried it yet .. wonder how it will look like if i shot the moon ..hmmm

any guy with experience with the meade video out to tv ?

rlow · Post by **rlow** » Thu Oct 12, 2006 2:16 pm

125mm is a good grab-and-go scope size for 3 factors: aperture, mount & tripod.

branzzz · Post by **branzzz** » Thu Oct 12, 2006 2:36 pm

may i know where did you order the 90mm? i initially ordered the 102mm and the min eq through vpost, but the order itself came up to 570SGD. i am now considering just the 90mm tabletop set. how was your shipping cost like

kayheem · Post by **kayheem** » Thu Oct 12, 2006 2:56 pm

I agree with rlow. The 5" SCT/MCT is just about the largest scope I consider really portable i.e. can take public transport with.

Any bigger means it is 'transportable' but not 'portable'/grab n go.

Canopus Lim · Post by **Canopus Lim** » Thu Oct 12, 2006 3:12 pm

Yup agreed (5 inch). Also, it has larger aperture and a maximum field of 2 degrees (with a 40mm widefield 2 inch eyepiece or with focal reducer and 32mm 1.25 inch plossl). Quite good overall in terms of portability and performance.

ariefm71 · Post by **ariefm71** » Thu Oct 12, 2006 4:06 pm

Yup agreed (5 inch). Also, it has larger aperture and a maximum field of 2 degrees (with a 40mm widefield 2 inch eyepiece or with focal reducer and 32mm 1.25 inch plossl). Quite good overall in terms of portability and performance.

Off-Topic:
For catadioptrics, to calculate the max field of view (without vignetting), you will need to measure the inside diameter of the scope's baffle tube, eg C5 baffle tube i.d. is 25mm, C8 is 38mm, C9.25 is 48mm, etc.

Treating the central baffle as the limiting field stop (true fov = field stop/scope's focal length * 1 radian), max fov of:
C5 at F10: 25/1250*57.3 = 1.15 degrees
C5 at F6.3: 25/787.5*57.3 = 1.8 degrees